The Government could invest billions of pounds in the Hitachi-owned Horizon project to build a new nuclear plant on Anglesey, under plans being discussed with Japan.

The proposal, which could see the UK fund 25pc of the project alongside significant loans from the Japanese government, is one of a number of options under consideration as the two countries seek to help Hitachi finance the plant.

Chancellor Philip Hammond, who met business leaders and Japanese officials in Tokyo on Thursday, said that Japanese government-related financing for the project could total £12bn but that negotiations were still on-going.

The likely cost of the proposed twin-reactor development at Wylfa has not been disclosed but a source close to the negotiations insisted a Reuters report that put the figure at £19bn was wide of the mark.