French energy giant EDF has withdrawn from a competition to construct mini-nuclear reactors in Britain, the company said on Tuesday.

EDF was one of six firms shortlisted in October last year for government support to deliver a new wave of nuclear reactors to provide cheaper and cleaner energy.

Two designs for small modular reactors (SMRs) from those submitted by GE-Hitachi, Holtec Britain, NuScale Power, Rolls-Royce and Westinghouse will be chosen by the end of the year.

The Conservative government which lost last week's general election set up the competition as part of its aim to derive up to a quarter of all UK electricity from nuclear power by mid-century.

Confirming its withdrawal, an EDF spokesperson said the company "remains committed to supporting the development of nuclear in the UK".

The company says it is rethinking its designs for small modular reactors, but added that "we will continue to work positively with the UK government to deliver a new nuclear future."

Labour, which won the election, has promised to extend the lifetime of existing nuclear plants, including the much-delayed and over-budget Hinkley Point C in southwest England.

EDF said in January that project could be delayed by four years, and cost as much as £8 billion ($9.5 billion) more than planned.

It had been due to become operational in June 2027 but that has now been pushed back to between 2029 and 2031, it added.

Labour also made developing SMRs part of its election pitch to the country, saying nuclear would help Britain achieve energy security and its aims of decarbonising the power grid by 2030.