Toshiba, the owner of the company with plans for a £10bn Cumbrian nuclear new build, has been demoted to the second tier of the Tokyo Stock Exchange.
The Japanese giant- which has taken full control of NuGen, which is behind proposals for a power station at Moorside, near Sellafield - has also seen its share price drop following the move.
It will no longer feature in the Nikkei 225 index of Japan's top public companies also faces the prospect of being delisted from the stock exchange altogether.
This switch has happened because Toshiba's liabilities exceeded its assets by several billion yen following a write-off for its American nuclear division Westinghouse Electric, due to provide three AP1000 reactors for Moorside.
It is attempting to raise funds by selling its memory chip division and is in discussions with other companies about selling its stake in NuGen, including South Korea's Kepco (Korea Electric Power Corporation).
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