Hitachi has announced it will suspend work on a multi-billion pound nuclear plant in the UK.
The decision follows speculation that it would scrap the £20bn Horizon nuclear facility because of concerns over rising construction costs.
The Japanese firm had been in talks with the UK government about funding since June.
The decision puts thousands of jobs at risk if the Wylfa Newydd plant in Anglesey, north Wales, is scrapped.
About 9,000 workers had been expected to be involved in building two nuclear reactors, which were due to be operational by the mid-2020s.
Hitachi said the decision would cost it an estimated 300bn yen (£2.1bn) in expenses, plus another 300bn yen as “extraordinary losses”.
It said it was suspending the project “from the viewpoint of its economic rationality as a private enterprise”.
Duncan Hawthorne, chief executive of Hitachi’s Horizon subsidiary, said the Anglesey site remained “the best site for nuclear development in the UK” and that the company would “keep the option to resume development in future”.
The new nuclear plant had been intended to have a generating capacity of 2,900 MW and have a 60-year operational life.
The decision puts the UK’s nuclear policy under fresh scrutiny.
In November, plans to build a nuclear power station at Moorside in Cumbria were halted after Toshiba announced it was winding up its NuGeneration subsidiary, which was behind the project.
The news was greeted with dismay by the Nuclear Industry Association.
Tom Greatrex, chief executive of the association, said it was “disappointing, not just for the Wylfa Newydd project but for Anglesey and the nuclear industry as a whole”.
“The urgent need for further new nuclear capacity in the UK should not be underestimated, with all but one of the UK’s nuclear power plant due to come offline by 2030.”
Justin Bowden, the GMB union’s national secretary for energy, said the decision raised “the very real prospect of a UK energy crisis”.
“While the government has had its head up its proverbial backside over Brexit, vital matters like guaranteeing the country’s future energy supply appear to have gone by the wayside.”
If the Wylfa Newydd project is scrapped, it leaves the Hinkley Point power station in Somerset as the only new UK reactor still being built.
The British and Japanese prime ministers met earlier this month, but did not discuss the Wylfa Newydd nuclear power plant.
“We have been working with them, but it will be a commercial decision for the company,” Prime Minister Theresa May said at the time.