Those involved in the alleged rigging of Britain's wholesale gas market will face the "full force of the law", Energy Secretary Ed Davey has warned.
Mr Davey promised firm action if there was any truth in allegations of gas price manipulation made by a whistleblower to the Financial Services Authority (FSA) and energy watchdog Ofgem.
He told MPs: "I see it as my job to protect consumers, not least the most vulnerable who can suffer the most when markets are abused."
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He said it was not possible to understand what impact any attempted manipulation, if proven, had on the market or prices paid by consumers.
But the Government had "absolute determination to clamp down on any abuse that is uncovered, wherever and by whoever".
Prime Minister David Cameron's official spokesman said that if the claims were true then regulators should come down very hard on those responsible. He added that energy price manipulation was totally unacceptable.
The 'big six' energy firms deny any involvement in attempts to fix the £300 billion market.