(Bloomberg) -- The U.K. government is being hit with two lawsuits from environmental groups who claim that its plans to radically decarbonize the economy in the coming decades fall short of what’s needed to avoid catastrophic climate change.

Friends of the Earth and ClientEarth will file separate suits in London this week challenging the lawfulness of the government’s much hyped net zero strategy. They’ll argue that much of the climate policy is predicated on unproven technology that’ll only delay the needed move away from a society that relies on fossil fuels.

In October, the U.K. government unveiled its plans to zero out emissions, ahead of hosting COP26 in Glasgow. Its watchdog, the Climate Change Committee, broadly welcomed the document but said there were a number of sizable omissions, including how the policies would be funded. 

It estimates the cost of the transition could be 1-2% of GDP by 2050, and moving away from fossil fuels will also hit tax revenue. 

Environmental law firm, ClientEarth, and Friends of the Earth both argue that the net zero targets are theoretical and don’t comply with the U.K.’s own climate change legislation.

“With characteristic sleight of hand the government has set out an imaginary pathway for reducing carbon emissions but no credible plan to deliver it,” Katie de Kauwe, a lawyer at Friends of the Earth, said.

The legal cases come at a time when a spike in the wholesale cost of gas has led to soaring energy bills in Britain. Politicians have called for the government slow on its decarbonization plans and increase the use of gas to ease the supply crunch, but others argue the best fix is to wean the U.K. off its gas addiction with more renewable energy.

“Government failure to deliver real climate action is resulting in higher bills for people,” Sam Hunter Jones, a lawyer at ClientEarth, said.

“The net zero strategy sets out specific, detailed measures we will take to transition to a low carbon economy,” a spokesperson for the Department for Business, Energy and Industrial Strategy said declining to comment on the suits. 

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