Revealed: The law you've never heard of that stops Britain building - and it's not even British

Downing Street wants to stop green activists from using a little-known international law to tie up major infrastructure projects in the courts using millions of pounds of taxpayer cash, Sky News can reveal.

An obscure international agreement known as the Aarhus Convention, named after Denmark's second city, is delaying some of the biggest industrial projects in the country.

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Around 80 cases a year are brought under the convention, Sky News has learned, which caps the costs of anyone bringing a case at £5,000 if the case is brought by an individual or £10,000 by organisations.

If this convention did not exist, costs would otherwise be awarded against a claimant for the losing side's legal fees in the event the claimant is unsuccessful - and could potentially run into the hundreds of thousands or even higher.

This means it's costing the taxpayer millions every year in legal fees - on top of what critics say is hundreds of millions of additional costs for developers as projects go through the courts.

The international law was brought in to allow those without deep pockets to challenge companies and governments they believe are breaking green laws.

However, it is causing big frustration in government.

Even some in the environmental movement believe it is being abused.

Modern lawfare

Campaigners who use it, however, say it is a vital tool to hold ministers to their green targets.

Many of the cases are brought by specialist human rights and environmentalist law firm Leigh Day, whose lead environmental lawyer told Sky News the convention "is extremely important to every claimant who's bringing an environmental case in this country".

These cases leave the taxpayer facing bills of millions of pounds, and developer costs reaching into the hundreds of millions because of delays to building work.

A source in Number 10 said the prime minister is personally affronted by this sort of use of the law, and it has been labelled "lawfare" - a derogatory term which means using the legal system to the detriment of one's opponents.

This week, a computer scientist and former Norfolk councillor is in court once more challenging the first carbon capture storage project on a gas-fired power station, which is due to be built on Teesside.

Andrew Boswell was the subject of a personal attack by the prime minister in the Daily Mail, who identified him as one of the "NIMBYs and zealots" for his legal challenges - including road schemes.

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Sky News took Mr Boswell to the site where building of the project, which is majority-run by BP, is due to take place once the court challenges are complete.

He said he was challenging the project on the grounds it would break the government's promises to adhere to carbon budgets under the Climate Change Act.

"People would be very surprised to hear they're going to build a gas-fired power station here," he said.

"They are going to put carbon capture and storage on it. But our analysis is that actually is not a good solution environmentally."

'We are holding the government to account'

Mr Boswell has so far lost the cases he has brought, and Sky News understands the delays to this project are costing £100m every three months.

Asked if this made him reconsider his decision to challenge the project, he said: "We are holding the government to account."

"The point is we have laws in this country, and we have a Climate Change Act, which we're legally enshrined to meet, and government ministers have been making decisions which aren't consistent with that," he added.

He said he and other environmental activists would not be able to bring such cases in the event that the Aarhus convention did not get the taxpayer to pay most of the costs against them in the event the case is unsuccessful.

"It would be very difficult for individual campaigners like myself and also the environmental groups and other groups who wish to go to court," he told me.

Projects of 'huge significance' being challenged

The law firm used by Mr Boswell, Leigh Day, brings several cases each year using the Aarhus Convention.

Carol Day, from Leigh Day, said about 80 cases were brought to the High Court per year on environmental issues.

"That doesn't sound like very many, but they are mostly very important projects of huge significance," she said, with "enormous implications for the protection of the environment".

A series of cases have been brought under the Aarhus Convention.

Mr Boswell himself took his case against proposed improvements to the A47 in Norfolk by National Highways all the way up to the Supreme Court.

In 2021, the Supreme Court overturned a block on Heathrow's expansion, a challenge brought under the convention capping the losers' costs at £10,000.

Activists point to the successful challenge by Sarah Finch.

Last year the challenge, by the self-employed writer resulted in a Supreme Court ruling that carbon emissions from burning fossil fuels should be factored into planning decisions.

The ruling has scotched an oil well near Gatwick and another near the village of Biscathorpe in Lincolnshire. The challenge would not have happened unless she knew her costs would be capped if she had lost.

Asked about whether it was right that millions of pounds of taxpayers' money are going to lawyers fighting cases that effectively delay big infrastructure projects for years, she insisted there would be "no challenge" if the projects "were made lawfully".

'We can't get things done'

Ben Houchen, the Tory Teesside mayor, whose Teesworks site will host the carbon capture and storage gas power station, said the system must change.

"The system has gone so far," he said, with "too many challenges".

"We can't get things done in this country. We have a democratically elected government that wants to deliver growth. It wants to deliver these types of investments. I've been elected on the promise of delivering these investments."

Mr Houchen called for "fundamental reform" to help "stop these activists from being able to stop any sort of economic growth and investment that creates jobs".

It appears Sir Keir Starmer agrees in principle. Whether he can reform an international treaty remains to be seen.

(c) Sky News 2025: Revealed: The law you've never heard of that stops Britain building - and it's not even British