The pound14.2-billion ($19-billion) investment will end "years of delay and uncertainty", the UK Treasury said in a statement, adding it would unlock a "golden age" of nuclear power to "boost the UK's energy security".

The latest injection is part of budget announcements by finance minister Rachel Reeves, who is due to detail her spending priorities on Wednesday, with defence and health at the forefront.

The government on Tuesday also announced that British manufacturer Rolls-Royce had won a competition to become the preferred bidder to build small modular nuclear reactors in the UK.

SMRs are aimed at cutting the costs and complexity of building nuclear power stations.

"The UK is back where it belongs, taking the lead in the technologies of tomorrow," Reeves said.

The government added that it would invest more than pound2.5 billion in nuclear fusion over five years in what it called a "record investment" for the nascent technology.

- Nuclear rollout -

The Labour government, which took over from the Conservatives in July, has promised to deliver "the biggest nuclear rollout program for a generation".

The UK has refocused on shoring up nuclear power since the start of the war in Ukraine, in the name of energy security and faced with a fleet of ageing power stations.

Britain's government is the majority shareholder in the Sizewell C plant being built in eastern England, after Chinese company CGN left the project and the other partner, French energy giant EDF, scaled back its involvement.

The UK is searching for another partner to join the project, then will deliver a "final investment decision", Prime Minister Keir Starmer's spokesperson said Tuesday.

The Sizewell C project, which comprises two EPR nuclear reactors each with 1.6 gigawatts capacity, could cost a total pound20-30 billion to build.

The sum could be even higher, according to some estimates which are disputed by the government and EDF, and it is not expected to start generating electricity until 2035.

"Today marks the start of an exciting new chapter for Sizewell C, the UK's first British-owned nuclear power plant in over 30 years," said joint managing directors of the project Julia Pyke and Nigel Cann.

The government wants to increase nuclear power's share of the energy mix, as it does not emit carbon dioxide into the atmosphere.

Starmer's government has pledged by 2035 to reduce UK greenhouse gas emissions by 81 percent on 1990 levels, under plans to reach net-zero by 2050.

The use of nuclear energy as an alternative to fossil fuels is highly controversial, however, with many environmental groups warning about safety risks and the disposal of nuclear waste.

The Sizewell C announcement has been met with anger by some local residents worried about the impact of the new plant on the local town of Leiston in Suffolk.

Near to Sizewell C is the Sizewell B nuclear power station which is due to close in 2035 -- and Sizewell A which is in the process of being decommissioned.

EDF is also building the Hinkley Point C nuclear power plant in southwestern England, although it has been blighted by delays and rising construction costs.

"The government's decision to move ahead with Sizewell C is fantastic news for Britain, its energy security and economic growth," said EDF Energy chief executive Simone Rossi.