The National Grid has halted its transmission line to a new nuclear power station after NuGen, the project's owner, said it is "hitting the pause button".
NuGen is conducting a strategic review of its Moorside reactor in Cumbria to assess the project's ownership and technology vender following recent setbacks.
France's Engie, which was backing the reactor with Toshiba, exited the joint venture last month following multi-billion pound losses from the Japanese firm's US nuclear unit raised questions over whether it could deliver on its UK commitments.
NuGen today announced chief executive Tom Samson met with shareholders and said: “At the end of March, it became clear we at NuGen had to take a step back due to these circumstances and revisit some fundamental elements on which we had been building the programme to deliver Moorside.”
Samson said the firm "hit the pause button" and launched a strategic review sanctioned by the board and in consultation with the UK government to explore a range of options, including new investors, technology and financing solutions to ensure the power station is delivered.
A spokesperson for the National Grid said: "In light of this, we have decided to pause our work to consent NuGen's connection and take the time to understand NuGen's programme to make sure our projects are aligned."
The Grid was planning to build a 102-mile power line connecting the proposed nuclear plant in Cumbria to the electricity transmission network. The new nuclear plant is set to deliver seven per cent of the UK's electricity from 2025.
"Despite this pause, we are confident the connection will still be ready when NuGen requires it and are continuing to work closely with them," the spokesperson said.
GMB, the union for energy workers, called on the government to step in after the latest in a string of setbacks at the £10bn Moorside reactor.
Justin Bowden, GMB national secretary, said: "How many kicks in the teeth for the desperately needed new nuclear plant at Moorside will it take to bring politicians of all colours to their senses?
“GMB has repeatedly called for the government to stop faffing and step in, questioning why ensuring our crucial energy requirements continues to be exposed to the obvious risks arising out of passing the responsibly to foreign govemnents and foreign companies."