Energy firms are warning that an attempt to extend a windfall tax to renewable energy would threaten the government's entire energy strategy.

Industry sources told the BBC it could destroy investor confidence ahead of key auctions for licences to develop new wind and solar projects.

Shares in firms that could be affected fell sharply on Tuesday, with Centrica down 11% and SSE 9% lower. An announcement on windfall taxes could come as soon as Thursday. However, the Treasury said no decisions had yet been made.

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