Energy experts have claimed that Sir Keir Starmer's plan to reach net zero by 2030 will cost £116 billion in additional investment.
This is more than double what it would cost to reach net zero by 2035, analysis by Auror Energy Research showed.
The figures, put together on behalf of Policy Exchange, saw Labour's goal dubbed "simply not feasible".
Thomas Cabot, research fellow at Policy Exchange and author of the paper, said: "Decarbonisation of the grid is essential to reaching our broader goal of economy-wide Net Zero by 2050.
The eye-watering cost of Sir Keir Starmer's 2030 net zero goal has been laid bare by energy experts, who argued that plan would require £116 billion in additional investment
PA
"Significant policy action and accelerated deployment of low carbon technologies – including enabling the construction of more onshore and offshore wind, major investments in the grid and bringing forward plans for at least one further large-scale nuclear plant by the end of 2025 – would help us to meet this goal more quickly."
Iain Mansfield, director of research at Policy Exchange, added: “To decarbonise the power grid by 2030 is simply not feasible.
“Given the state of the public finances, it is hard to see how any Government could find the additional £93 billion required – but even if the money were made available, it is simply not possible to build new renewable generation at the pace required.
“Tackling climate change is a priority – but we must do so on the basis of targets that can actually be delivered.”
Starmer, on a trip to Wales today, will speak about Labour’s plans to boost Britain’s energy security.
Discussing plans for a publicly owned clean energy company, the Labour leader is expected to say that Britain must "take back control of our national energy security".
Starmer will say that Great British Energy can "get Putin’s boot off our throat".
Yesterday, he said: "Great British Energy will be built to last, and the wind farms, carbon capture and all the good jobs that go with it will be built to last, too.
"It will be a legacy of the next Labour Government. Here in Wales, the potential for offshore wind is enormous, and the UK Tory government is squandering it.
"With public investment through Great British Energy we can unlock billions more in private investment to turbocharge jobs and growth for Wales."
In February, Labour slashed billions of pounds a year from its green prosperity plan in a significant U-turn, claiming that the state of the economy meant that it had become unaffordable.
The saving was made by radically scaling back an ambitious "warm homes plan" to insulate millions of homes over the next decade.
But a Labour Spokesperson said: "After 14 years, the government is still not on track to meet it's clean power targets. Britain cannot afford five more years of Rishi Sunak’s inaction.
“The Conservatives have blocked onshore wind, crashed the market for offshore wind, stalled on energy efficiency, and failed to tackle an out-of-date planning system that has meant holding back over £200 billion of private sector investment.
“Labour's Green Prosperity Plan will make our country energy secure with investment in homegrown clean power to cut bills and boost our national energy security. Labour will crowd in billions in private investment and bring good jobs to Britain’s industrial heartlands.”
