Campaigners have scored a second legal victory against the Government over its “reckless and inadequate” climate policies after a High Court judge ruled it acted unlawfully by approving a plan to cut carbon emissions.

Environmental charities Friends of the Earth and ClientEarth, and the Good Law Project, took joint legal action against the Department for Energy Security and Net Zero (DESNZ) over its decision to approve the Carbon Budget Delivery Plan (CBDP) in March 2023, claiming it had not shown how the plan could be achieved.

The plan aims to show how the country will achieve targets set out in the sixth carbon budget, which runs until 2037, as part of wider efforts to reach net zero by 2050.

Lawyers for Friends of the Earth demanded “credible and lawful new action” following the ruling, with ClientEarth calling for “no more pie in the sky”.

It follows a victory for the same three groups against the Government in the High Court over climate policy in 2022, with the DESNZ stating it would redraft the CBDP within 12 months as a result of the decision.

In his judgment, Mr Justice Sheldon said the decision to approve the plan by the then secretary of state, Grant Shapps, was “simply not justified by the evidence”.

He said: “If, as I have found, the secretary of state did make his decision on the assumption that each of the proposals and policies would be delivered in full, then the secretary of state’s decision was taken on the basis of a mistaken understanding of the true factual position.”

The three groups previously defeated the Government in legal action over its Net Zero Strategy in 2022.

In that case, a different judge ruled the Government’s plan was unlawful as ministers were not properly briefed on how individual policies would help meet climate targets set out in the sixth carbon budget, as required by the 2008 Climate Change Act (CCA).

In the CBDP case, the groups argued at a hearing in February that approving the plan was unlawful as Mr Shapps lacked information on whether individual policies could be delivered in full.

They claimed Mr Shapps had no or inaccurate information from different Government departments about the risks related to enacting climate policies under the plan, which gave a “misleading summary” of whether they could be put in place.

David Wolfe KC, representing FoE, told the court some “risk tables” – used to demonstrate the risks associated with delivering each policy – were “recast” to remove information about whether plans could be implemented.

The tables were not shared with Parliament, climate bodies or the public, meaning the plan could not be properly scrutinised, the court heard.

Lawyers for the Government said Mr Shapps had “sufficient information” which “rationally supported” his decision.

But in his 50-page ruling, Mr Justice Sheldon said the minister “could not evaluate for himself” which policies in the CBDP would fail and which would be delivered based on the information provided.

He said the details in the draft plan were “vague and unquantified” and did not provide Mr Shapps with “sufficient” information on whether the proposals should be approved.

Speaking following the ruling, Friends of the Earth lawyer Katie de Kauwe said: “This is another embarrassing defeat for the Government and its reckless and inadequate climate plans.

“It shows the strength of the Climate Change Act – brought into force after a successful campaign led by Friends of the Earth and the backing of an overwhelming majority of MPs – to hold the Government of the day to account for meeting its legal requirements to cut emissions.

“We urgently need a credible and lawful new action plan that puts our climate goals back on track and ensures we all benefit from a fair transition to a sustainable future.

“Meeting our domestic and international carbon reduction targets must be a top priority for whichever party wins the next general election.”

Sam Hunter Jones, a senior lawyer for ClientEarth, said: “The courts have now told the UK Government not once, but twice, that its climate strategy is not fit for purpose. This time the court made it emphatically clear: the Government cannot just cross its fingers and hope for high-risk technologies and uncertain policies to plug the huge gaps in its plans.

“No more pie in the sky – this judgment means the Government must now take credible action to address the climate crisis with a plan that can actually be trusted to deliver and with numbers that can be relied on.

“The good news is that with crisis comes opportunity. As its own expert advisers have repeatedly said, the Government has a golden opportunity to reduce emissions with actions that will also create jobs, improve services and bring down household bills.”

Emma Dearnaley, legal director of Good Law Project, said: “This welcome ruling shows that the law is our best, and often last, line of defence against a Government that is failing to act as it must to address the climate emergency. We will continue to use it to push for accountability and greater ambition.”

In response to the decision, a DESNZ spokesperson said: “The UK can be hugely proud of its record on climate change. Not only are we the first major economy to reach halfway to net zero, we have also set out more detail than any other G20 country on how we will reach our ambitious carbon budgets.

“The claims in this case were largely about process and the judgment contains no criticism of the detailed plans we have in place. We do not believe a court case about process represents the best way of driving progress towards our shared goal of reaching net zero.”

While the CBDP remains Government policy, the DESNZ said it will be redrafted.