Britain could face £4TRILLION in climate reparations Labour bows down to United Nations court

Britain could face a £4trillion climate reparation bill if the Government bows down to a UN court, a think-tank says.

Lawyers and activists are poised to launch a wave of litigation to “punish the West for the Industrial Revolution”, it warned. The UK could also be forced to stop drilling in the North Sea because of the “unprecedented” finding on climate change from the International Court of Justice (ICJ), according to Policy Exchange.

Its paper urged the Government to stand up to the court and publicly acknowledge the ICJ's opinion is not legally binding. In July 2025, the ICJ concluded countries have duties to prevent climate harm and can be sued for compensation if they fail.

Although the ICJ’s conclusion was an “advisory opinion", meaning it is not legally binding, the Policy Exchange authors warn this could make little difference to activists and interested parties. They point to the Chagos Islands case – dubbed the "surrender deal" – as an example.

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In 2019, the ICJ issued an Advisory Opinion that the UK should end its administration of the islands “as rapidly as possible”. It was not legally binding – but the Government chose to hand over the islands in any event.

It maintained, without the agreement, the country could face future, legally binding, rulings, putting the Diego Garcia military base at risk. The Policy Exchange authors, three legal academics, suggest this “supine” approach towards the ICJ could see the UK sued for trillions of pounds on climate grounds.

Cambridge University's Dr Tom Grant, one of the report authors, wrote: “The Climate Change Advisory Opinion is a significant, and regrettable, development in international law. It exposes the UK to a new wave of litigation and to colossal financial risks.”

The ICJ opinion goes beyond the obligations in the Paris Agreement on Climate Change, to which Britain has agreed, the authors say. Despite this, in May this year, the UK endorsed the Advisory Opinion of the ICJ.

This was an example of “prioritising the advisory opinions of an international court over the UK’s national interests," the think-tank says. Dr Grant and his co-authors, Dr Yuan Yi Zhu and Professor Richard Ekins, warn it could end up costing the country £4trillion.

“The Advisory Opinion seems to open the door for lawsuits against States which generated greenhouse gas emissions in the past,” they write. “The United Kingdom, as birthplace of the Industrial Revolution, is the most obvious target for such suits.”

They continue: “It seems almost certain that the UK will be a target for litigation on the basis of the Climate Change Advisory Opinion.”

They cite a paper in journal Nature Sustainability, which calculated high-carbon countries owe their low-carbon peers $192trillion in climate change reparations.

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“If judges held the UK responsible for 3 per cent of all emissions, this would amount to a sum of US$5.76 trillion (£4.24 trillion)”, they warn. “The extraordinary magnitude of the liability to which the Advisory Opinion exposes the UK does not seem to have registered in Westminster and Whitehall, let alone among the wider British public. There is certainly no evidence that the Government or Parliament has taken the measure of the problem or done anything to limit the UK’s exposure.”

They say the ICJ opinion has now become “a point of reference for lawyers concerned about climate change”. A failure by the Government to treat the view as non-binding would have serious repercussions on energy policy.

The ICJ explicitly found granting fossil fuel licences, or even failing to shut down existing production, "may constitute an internationally wrongful act". This could put North Sea exploration at risk.

“The Climate Change Advisory Opinion addresses even more consequential issues than that on the Chagos,” says the report. “The Government’s Net Zero aims, the ongoing energy crisis, and calls to open oil and gas production at the Rosebank and Jackdaw fields in the North Sea rightly now absorb policymakers and the general public in urgent debates. The Climate Change Advisory Opinion, if treated as a binding legal judgment, will not help inform those debates. It will shut them down.”

The authors call for the UK to withdraw from the compulsory jurisdiction of the ICJ. This would bring the country into line with the other permanent members of the UN Security Council.

It should also publicly reaffirm the non-binding nature of ICJ advisory opinions and take steps to stop other treaties being “weaponised” in the name of climate, they say. Senior justices and politicians used forewords to welcome the Policy Exchange report.

Alexander Downer, former minister for foreign affairs and Australian high commissioner to the UK, said: “Action to combat climate change must not be turned into an occasion to extort monies from industrialized countries. Yet this is exactly what has happened. By making grand claims about what international law allegedly mandates of states, the ICJ has given a gloss of legitimacy to the agenda of climate activists for whom punishing the West for the Industrial Revolution is as important, if not more so, than real climate action in this century.”

Former Supreme Court judge Lord Sumption wrote: “The function of a court of law, whether international or domestic, it to declare the law as it is, and not as its judges conceive that it ought to be. The International Court of Justice has for most of its history been a distinguished court whose judgments commanded respect. Unfortunately, as Policy Exchange’s new report eloquently lays out, the radical departure from its proper role in some of its recent decisions undermines the whole basis on which it can continue to claim the respect of the international community.”

Lord Verdirame KC, barrister and Professor of International Law, King’s College London, commented: "No responsible British government can ignore the litigation risks that result from the developments in the climate change area. This paper’s analysis of those risks should sound a warning in Whitehall.”

Former Lord Chief Justice of England and Wales, Lord Burnett, and former Foreign Secretary, Sir Malcolm Rifkind, also backed the Policy Exchange paper. Lord Burnett stated: “Climate change is a real and urgent problem; so too is the expanding use of the ICJ’s advisory jurisdiction.”

The Government has been approached for comment.

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