The government has announced it will become the main shareholder in the new Sizewell C nuclear plant.
It has confirmed taxpayers will take a 44.9% stake in the project which will also be funded by four other companies; EDF, Centrica, La Caisse and Amber Infrastructure.
Downing Street had already committed £14.2bn of investment to build the new Sizewell C nuclear plant on the Suffolk coastline, ahead of the Spending Review.
The cost of the project, revealed on Tuesday, is now £38bn - the last official figure was for £20bn.
Alison Downes, director of pressure group Stop Sizewell C, said previously ministers had not "come clean" about Sizewell C's cost, because "negotiations with private investors are incomplete".
Sizewell C is expected to create 10,000 direct jobs, thousands more in firms supplying the plant and generate enough energy to power six million homes, the Treasury said.
Energy Secretary Ed Miliband said: "It is time to do big things and build big projects in this country again and today we announce an investment that will provide clean, homegrown power to millions of homes for generations to come.
"This government is making the investment needed to deliver a new golden age of nuclear, so we can end delays and free us from the ravages of the global fossil fuel markets to bring bills down for good."
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