1. Introduction

The Office of Gas and Electricity Markets (Ofgem) is the administrative office through which the Gas and Electricity Markets Authority (GEMA) performs its regulatory functions in Great Britain. GEMA/Ofgem regulates electricity and gas markets under legislation including the Electricity Act 1989 and Gas Act 1986. Its functions include licensing, price regulation, network regulation, enforcement, market rules and consumer protection. The statutory framework places particular importance on protecting the interests of existing and future consumers and, where appropriate, promoting effective competition. (Bailii)

Because Ofgem exercises statutory and public powers, its decisions are subject to judicial review. Judicial review does not ordinarily allow the court to substitute its own economic or regulatory judgment for that of Ofgem. Instead, the court examines whether Ofgem acted lawfully, fairly, rationally and within the limits of its statutory powers.

2. Meaning of Judicial Review of Ofgem Decisions

Judicial review is concerned primarily with the legality of the decision-making process and the lawfulness of the decision, rather than whether the court considers the regulatory decision to be economically preferable.

A challenge to an Ofgem decision may therefore concern:

Illegality or ultra vires – Ofgem acted outside its statutory powers.

Error of law – Ofgem misunderstood or incorrectly applied the governing legislation.

Procedural unfairness – Ofgem failed to follow a fair consultation or decision-making process.

Failure to take relevant considerations into account.

Taking irrelevant considerations into account.

Irrationality or unreasonableness.

Failure to give adequate reasons, where a duty to give reasons applies.

Legitimate expectation.

Disproportionality, particularly where protected rights or applicable legal principles require proportionality.

In appropriate circumstances, improper purpose or abuse of power.

The intensity of review can vary according to the nature of the decision. Courts are generally cautious about interfering with decisions involving highly technical, economic or regulatory judgments.

3. Statutory Framework Governing Ofgem

The legal foundation is principally found in the Electricity Act 1989 and Gas Act 1986.

Ofgem/GEMA's principal statutory objectives concern the interests of existing and future consumers, including the promotion of effective competition where appropriate. The regulatory framework also contains duties concerning matters such as security of supply, financeability, environmental considerations and network regulation. (Bailii)

This creates an important principle for judicial review:

Ofgem must exercise the discretion Parliament has given it, but the court will normally respect the regulator's specialist judgment within the lawful boundaries of that discretion.

Consequently, an unsuccessful commercial outcome does not automatically establish unlawfulness.

4. Grounds for Judicial Review of Ofgem

A. Illegality and Ultra Vires

The first question is whether Ofgem had legal authority to make the decision.

A claimant may argue that Ofgem:

misunderstood its statutory powers;

acted beyond the scope of its licence-regulation powers;

applied the wrong statutory test;

failed to comply with a mandatory statutory duty; or

pursued a purpose that Parliament did not authorise.

Exoteric Gas Solutions Ltd v GEMA

In R (Exoteric Gas Solutions Ltd) v Gas and Electricity Markets Authority, the claimant challenged Ofgem's decision not to take immediate enforcement action against Transco and instead to conduct an industry-wide investigation. The case illustrates that a regulatory decision not to pursue a particular enforcement route can itself be challenged by judicial review. (vLex)

The challenge ultimately did not succeed; contemporary parliamentary evidence records that the Authority's decision was upheld and the judicial review dismissed. (UK Parliament)

The case demonstrates the courts' reluctance to dictate to an expert regulator precisely how it should exercise its enforcement discretion, provided that the discretion is exercised lawfully.

5. Failure to Take Relevant Considerations into Account

Ofgem must identify and consider matters which Parliament requires it to consider and, depending on the statutory framework, other considerations that are legally material.

A claimant may argue that Ofgem:

ignored important evidence;

misunderstood material evidence;

failed to consider an alternative;

failed to consider the consequences of its decision; or

considered something legally irrelevant.

Peak Gen Top Co Ltd v GEMA

A particularly important case is:

R (Peak Gen Top Co Ltd and others) v Gas and Electricity Markets Authority [2018] EWHC 1583 (Admin).

The claim concerned Ofgem's decision concerning electricity transmission charging arrangements for embedded generators. The claimants alleged, among other things, that Ofgem had:

breached the principle of non-discrimination; and

failed to take account of material considerations or facts.

The claimants were refused permission to rely on irrationality as a separate ground. (Bailii)

The case demonstrates that failure to consider a material matter can provide a distinct public-law ground, but the claimant must establish more than simply showing that another regulatory approach was possible.

6. Irrationality and Unreasonableness

The traditional public-law principle associated with Wednesbury unreasonableness remains relevant.

However, in regulatory cases the practical threshold can be demanding because Ofgem frequently deals with:

complex economic evidence;

network investment;

electricity pricing;

market design;

transmission charging;

technical data; and

competing statutory objectives.

Courts therefore generally avoid substituting their own economic judgment for that of the specialist regulator.

Npower v GEMA [2018] EWHC 3576 (Admin)

Npower v GEMA [2018] EWHC 3576 (Admin) is an important example.

The case involved a challenge to an Ofgem direction concerning a trial relating to customer responses and the regulatory framework. The claimant raised, among other grounds:

failure to give reasons;

irrationality;

proportionality;

improper purpose; and

other public-law objections.

The High Court rejected the irrationality challenge and ultimately rejected the substantive grounds of challenge. (Ofgem)

The judgment is significant because it demonstrates that the mere existence of an alternative regulatory approach does not establish irrationality.

7. Duty to Give Reasons

Reasoned decision-making is particularly important in energy regulation because Ofgem decisions can have substantial consequences for:

network companies;

generators;

suppliers;

consumers;

investors; and

competitors.

In Npower v GEMA, the court considered the adequacy of Ofgem's reasons. The judgment referred to the principle that reasons must adequately explain the decision and address the principal controversial issues, with the required degree of detail depending on the circumstances. (Ofgem)

The court emphasised the importance of whether the information supplied leaves genuine doubt as to what the regulator decided and why.

Thus, a decision will not necessarily be unlawful merely because the reasons are lengthy or technical; the critical question is whether the reasons permit the affected party and the court to understand the basis of the decision.

8. Procedural Fairness and Consultation

Ofgem frequently reaches decisions following:

consultation;

publication of proposals;

receipt of representations;

impact assessment;

consideration of stakeholder evidence; and

final decision.

Where consultation is required, Ofgem must comply with applicable legal requirements and basic principles of fairness.

A claimant may therefore argue that:

the consultation was misleading;

insufficient information was provided;

inadequate time was given;

Ofgem failed genuinely to consider responses; or

Ofgem departed substantially from its proposal without giving affected parties a fair opportunity to respond.

The precise requirements depend on the statutory framework and circumstances.

9. Legitimate Expectation

Judicial review can also arise where Ofgem's previous representations, policies or established practices allegedly created a legitimate expectation.

A claimant might argue that Ofgem:

promised to follow a particular procedure;

represented that a particular policy would apply;

departed from an established representation without adequate justification.

However, regulatory policy is capable of changing, particularly where Ofgem is required to respond to changing market conditions or statutory objectives.

Therefore, a legitimate-expectation claim requires careful examination of:

the nature of the representation;

whether it was clear and unequivocal;

whether reliance or unfairness is established; and

whether there is sufficient public-interest justification for departure.

10. Judicial Review and Ofgem's Technical Expertise

A central feature of Ofgem judicial review is the relationship between judicial supervision and regulatory expertise.

Courts generally recognise that Ofgem possesses specialist knowledge concerning:

electricity markets;

network economics;

tariff structures;

price controls;

transmission charging;

investment incentives;

consumer behaviour; and

financial modelling.

Accordingly, the court normally asks whether the decision falls within the range of legally permissible regulatory choices rather than asking:

"Would the court have reached the same economic conclusion?"

This principle is particularly important in price-control litigation.

11. Ofgem Decisions and Statutory Appeals to the CMA

An important distinction must be made between direct judicial review of Ofgem and the special statutory appeal mechanisms available for certain Ofgem decisions.

For some price-control and licence-modification decisions, legislation provides an appeal to the Competition and Markets Authority (CMA).

The CMA may therefore examine the substance of an Ofgem decision under the applicable statutory grounds. A subsequent judicial review may then challenge the CMA's determination, rather than simply inviting the High Court to reconsider Ofgem's original decision.

Wales & West Utilities Ltd v CMA [2026] EWHC 99 (Admin)

The modern importance of this distinction is illustrated by R (Wales & West Utilities Ltd) v Competition and Markets Authority [2026] EWHC 99 (Admin).

The case concerned the RIIO-2 price-control framework and a challenge to the CMA's determination of an appeal from GEMA's price-control decision. The High Court considered questions concerning the correct legal approach to reviewing GEMA's regulatory judgment and dismissed WWU's judicial review challenge. (Bailii)

The judgment explains that the CMA's statutory role is more substantive than ordinary judicial review, but it is still not simply a complete rehearing in which the CMA substitutes its preferred regulatory decision for GEMA's. (Bailii)

This creates a layered system:

Ofgem/GEMA decision → statutory appeal to CMA where available → judicial review of CMA decision.

12. SSE Code Modification Litigation

Another useful example is the litigation concerning SSE's challenge to decisions relating to electricity transmission charging code modifications.

The CMA's published case history records that SSE challenged the CMA's determination concerning appeals against Ofgem's decisions. The High Court allowed part of SSE's judicial review, resulting in quashing orders concerning aspects of the CMA's decision; the Court of Appeal subsequently altered the outcome. (GOV.UK)

This illustrates an important principle:

Judicial review can correct legal errors in the regulatory appellate process without requiring the court itself to become the electricity-market regulator.

13. Alaska Energy Ltd v GEMA

In Alaska Energy Limited v GEMA, the claimant challenged Ofgem decisions concerning the assessment period for supply-licence applications and the removal of tacit authorisation.

The grounds included:

ultra vires;

failure to give reasons;

legitimate expectation; and

unreasonableness.

The claim was dismissed at the permission stage because it was brought out of time. The judge nevertheless considered aspects of the merits and concluded, among other things, that it was unarguable that Ofgem was unjustified in temporarily pausing the licensing process while reviewing the regulatory framework. (Ofgem)

The case therefore demonstrates two important features of judicial review:

Procedural requirements such as time limits matter, and

Courts may recognise considerable regulatory discretion where Ofgem is responding to significant changes in market conditions.

14. Remedies

Where an Ofgem decision is found unlawful, the court has public-law remedies including:

Quashing Order

The court may quash the unlawful decision and require the regulator to reconsider the matter lawfully.

Mandatory Order

The court may require a public authority to perform a legal duty.

Declaration

The court may formally declare the legal position.

Prohibitory Order

In appropriate cases, the court can restrain unlawful action.

Injunction

An injunction may sometimes be available, depending on the circumstances.

The remedy is discretionary. A finding of legal error does not necessarily mean that the court will itself make the substantive regulatory decision.

15. Key Case Law at a Glance

The historical Ofgem case record also identifies Teesside Power, Scottish Power Energy Management, Exoteric Gas Solutions and Drax/ScottishPower/Teesside Power as significant judicial-review proceedings involving GEMA. (UK Parliament)

16. Conclusion

Judicial review of Ofgem decisions performs an important constitutional function in energy regulation. Ofgem has substantial technical and economic expertise, but that expertise does not place its decisions beyond judicial supervision.

The courts principally ensure that Ofgem:

acts within its statutory powers;

applies the correct legal framework;

fulfils mandatory statutory duties;

considers relevant matters;

avoids irrelevant considerations;

follows fair procedures;

provides adequate reasons where required;

does not act irrationally or for an improper purpose; and

respects applicable principles of legitimate expectation and proportionality.

At the same time, judicial review is not ordinarily an appeal on the merits. The court normally does not decide what electricity tariff, transmission charge, price control or market rule would have been economically optimal. Its constitutional role is to determine whether the regulator's decision was lawfully reached and legally defensible.

The modern Wales & West Utilities litigation illustrates this institutional balance particularly clearly: regulatory decisions may be subject to substantive statutory appeal mechanisms before reaching the judicial-review stage, while the High Court continues to supervise the legality of the regulatory process. (Bailii)

Thus, judicial review of Ofgem can be understood as a mechanism of accountability without judicial substitution: courts enforce the boundaries of lawful regulation while generally leaving technically and economically specialised judgments to the regulator entrusted with making them.