Approval by the UK Government of the planned Sizewell C nuclear plant was ruled lawful by London’s Court of Appeal on Wednesday, dismissing a legal challenge from environmental groups.

Campaign groups Together Against Sizewell C (TASC), Suffolk Coastal Friends of the Earth and Stop Sizewell C had initially requested a review into the environmental impacts of the nuclear project, arguing that the need for a huge water supply for the plant hadn’t been properly considered during the initial approval process in July 2022.

A spokesperson for Sizewell C said in a statement: “After two previous High Court dismissals on this issue, we welcome today’s judgment and now look forward to the next step for this project.

“Sizewell C will play a key role in Britain’s clean energy future, and this judgment comes at an exciting phase in the project’s development: following excellent progress of pre-commencement work this year, we are now looking forward to beginning the construction phase in 2024,” they added.

Sizewell C is being built by French state-owned nuclear major EDF, which will also operate the plant once construction is finished. Electrical output from the plant is expected to be approximately 3.2GW, with both reactors operational in mid-2034.

TASC said in a joint statement with Suffolk Coastal Friends of the Earth and Stop Sizewell C on X, formerly Twitter, that the groups are “dismayed” by the court’s decision. “We struggle to understand how the potable water supply that… SZC [Sizewell C] is totally reliant on for its 60 years of op[eration] can be considered lawfully, or indeed rationally, as a separate project,” the statement added. The groups also warned that “betting taxpayers’ money” on nuclear power “will not work”.

To date, the government has poured £700m ($868.13m) into the project, a sum that has built up through sporadic investment announcements as costs continue to rise beyond initial estimates. In May last year, one month before ministers were due to vote on the project’s approval, the Guardian reported that Sizewell C could cost UK taxpayers “more than double” government estimates and take an additional five years to build.

The UK’s other flagship nuclear project, Hinkley Point C, now deep into construction, has similarly faced criticism for its decades-long delays and soaring costs.