Plans for a new nuclear power station in Cumbria are likely to be scrapped after a key backer pulled out, creating a major hole in the government’s nuclear strategy.

Two industry sources close to the process said Toshiba had privately decided to quit the consortium behind the planned Moorside plant, echoing sources who told Reuters and the Wall Street Journal that the Japanese company was withdrawing from new nuclear projects in the UK.

Toshiba said last month it was reviewing all its nuclear business abroad after suffering a multibillion-dollar writedown on its US business. It has promised to provide more details about its intentions when it publishes results on 14 February.

The French energy firm Engie, which is Toshiba’s partner in the NuGen consortium, has long been seen as wanting to get out of the project. Its chief executive said last year the future did not lie in nuclear power.

The company said that, along with Toshiba, it was seeking new investors to finance the Moorside plant, which are reported to include Korea Electric Power Corporation (Kepco).

Senior figures in the industry urged the government to start discussions with the South Koreans immediately to safeguard the power station if Toshiba left NuGen.

“Any potential investor in that project is going to need to have very direct reassurance from the government; even if they are just starting an exploratory period, they are welcomed,” said Tim Yeo, the chairman of the pro-nuclear group New Nuclear Watch Europe.

The former Conservative MP said ministers should even consider taking a direct stake in the Moorside plant. Such an interventionist approach would have been anathema in recent years but appears more credible after recent leaks revealed the government was considering taking a stake in another new nuclear plant, at Wylfa in Wales.

Unions also called for the government to step in with funding to save the plant if Toshiba pulled out. “It looks increasingly like bad business investments may have busted Toshiba’s role in a new nuclear facility at Moorside in Cumbria,” said Justin Bowden, the GMB’s national secretary for energy.

Moorside, near Sellafield, is a key part of the government’s hopes for a new fleet of power stations to fill the UK’s energy gap in the next decade as coal plants and ageing atomic plants close.

The only one to be approved so far is EDF’s £18bn Hinkley Point C plant in Somerset, which was made financially possible through subsidies to be levied on household bills. The government hopes new plants will be built at Wylffa, Sizewell, Bradwell and Oldbury.

Of Moorside’s three mooted reactors, Paul Dorfman, from the Energy Institute at University College London said: “These are really big pieces of kit. If and when plans for Moorside fail, this leaves an existential gap in UK energy policy.”

Toshiba’s chief executive, Satoshi Tsunakawa, signalled last week that new nuclear projects would be reviewed in response to the anticipated multibillion-dollar writedown related to the purchase of a nuclear construction and services business by its US subsidiary, Westinghouse Electric.

No official decision has been made on NuGen.

“At this moment, we can only say that we are reviewing the future of our nuclear power business outside Japan, but nothing has been decided at this time,” the company told the Guardian.

A spokesman for Engie said the company “continues to evaluate the site and design of the NuGen Moorside facility”.

Theresa May told parliament earlier this week that the government was committed to new nuclear plants. A spokesman for the government said it was “working closely with a number of developers”.