Boris Johnson has approved funding for a new nuclear power station at Sizewell in Suffolk in the final weeks of his premiership, but some of Liz Truss’s senior allies are split over the decision. The prime minister and the chancellor, Nadhim Zahawi, approved financing for the construction of two new reactors known as Sizewell C, enabling private funding of about £20-30bn to be raised. However, Simon Clarke, another key Truss ally and a Treasury minister, warned in a letter leaked to the Sunday Times that the decision could limit Truss’s economic vision. In the letter, he said the costs of Sizewell C were “sufficient to materially affect spending and fiscal choices for an incoming government, especially in the context of wider pressures on the public finances”. In an article for the Mail on Sunday, Kwasi Kwarteng stressed the need to “crack on with more nuclear power stations” in order to increase Britain’s energy security. He gave development consent for Sizewell C in July, but negotiations over the government’s investment decision had been ongoing. A Whitehall source said Boris Johnson had taken the decision to press ahead with Sizewell several weeks ago. However, he dismissed the idea that the move would tie the hands of the next prime minister, following reports that the Truss campaign was worried that it was irreversible. “In the next few weeks, we will announce a government investment decision on Sizewell C where the government formally commits to the project’s financing. It allows the project to raise private capital in the markets. But it’s only at the point of the final investment decision in early 2023 that the government would formalise any equity share.” Johnson’s decision over Sizewell was challenged by a campaign to stop the nuclear reactor being built. A spokesperson for the campaign, Stop Sizewell C, said: “Whatever way you look at it, this is a very dodgy decision. Has it been made by a lame duck PM who is not supposed to tie the hands of his successor, or was it in fact made before Sizewell C was granted planning consent, lending serious weight to our conviction that this was a prejudiced, political decision? “Our next prime minister should call Sizewell C in. There are so many better ways to spend billions of pounds of taxpayers’ money than on a project that won’t light a single lightbulb for at least a decade.” Truss has not stated a clear position on Sizewell C, but hinted last year at concerns about the involvement of China’s state-owned energy company, CGN, as part of a consortium providing funding for the preparatory work at the nuclear plant. She told the Telegraph at the time: “I think it’s very important that we don’t become strategically dependent and I think it’s important that we make sure that we’re working, particularly in areas of critical national infrastructure, with reliable partners.” EDF, the French state energy firm, worked with CGN on the first phase of the project for a new nuclear power station to sit alongside Sizewell B, which is operational, and Sizewell A, which is being decommissioned. The UK government is keen to ease CGN out, however, over concerns about Chinese involvement in sensitive assets. Johnson’s government has already put up £100m of funding this year to support the development of Sizewell C.