The business secretary has approved the application for the development of the new plant in Suffolk.
It has been estimated the nuclear power station will generate enough low-carbon electricity to power six million homes.
The Planning Inspectorate said it would help the UK along the way to achieving net-zero emissions. The approval comes nearly two years after the application for Sizewell C to be built was submitted to the government agency.
The Planning Inspectorate had recommended its approval only if the water supply strategy was resolved, and more information provided to reassure ministers it was in line with habitats regulations.
The business secretary approved the project on Wednesday.
Campaigners against the site hit out at the decision, vowing to keep fighting against its development.
“The government has been forced to ram through a damaging project to shore up its energy strategy, but the fact that the Planning Inspectorate recommended Sizewell C be refused consent is a huge victory for all of us,” campaign group Stop Sizewell C said.
“The wrong decision has been made, but it’s not the end of our campaign to Stop Sizewell C.”
Hundreds marched against the plant back in May, which has faced backlash from campaigners worried about the potential impact on water supply, biodiversity and coastal erosion.
In a tweet on Wednesday, Mr Kwarteng said the move was part of a “big week of energy security”.
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