The British government approved the plant in July, and talks are continuing to raise money for it, which is not expected to be operational until 2030.  Mr Johnson said the war in Ukraine, which had pushed up gas prices, showed the UK needed new nuclear capacity.  In his last major policy speech before stepping down, he argued that the reluctance of previous governments to support nuclear power had led to higher energy bills.  Describing his predecessor as "short-sighted", Mr Johnson added: "It's called short-termism.  This is a long-term phenomenon that our politicians cannot transcend the political cycle."  "Let's think about the future, let's think about our children and grandchildren, the next generation,"  

Tom Greatrex, head of Britain's Nuclear Industry Association, welcomed Mr. Johnson's comments,  Calling it "a major step in the direction of cutting gas, cutting energy bills and creating stable, secure, well-paid jobs for people up and down the country in Britain".  However, Caroline Lucas, the former Green party leader, said Sizewell C was "expensive, painfully slow to build and would pose huge unnecessary risks".  She added that "significant upfront costs" would be passed on to consumers.  

The anti-nuclear Stop Sizewell group said: "When every penny counts, it would be completely wrong to tie the next chancellor and billions of taxpayers' money to a damaging project with ballooning costs, long construction times, fail-prone technology and very uncertain long-term supplies."  The group urged Johnson's successor to review the project and focus on "cheaper, faster renewable energy and insulation."  

The war in Ukraine has pushed up gas prices and renewed concerns about energy security in the UK.  The energy crisis is likely to dominate whoever succeeds Mr Johnson as prime minister.