Energy regulator Ofgem has proposed that the Big Six energy firms should be investigated by the Competition and Markets Authority.
In an open letter to Britain's main energy suppliers, the regulator's chief executive officer Dermot Nolan said they were concerned that companies were "not passing on savings to customers".
He said: "A concern that savings were not being passed on to customers was one of the reasons why we have proposed a referral of the energy market to the Competition and Markets Authority for investigation."
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Consumer prices have rocketed by 58% since 2003, with the UK industry paying the biggest bills in Europe.
Friday will be a much calmer day for many, with the weather set to remain dryer with sunny periods and much lighter winds than on Thursday.
Teachers and managers in particularly are putting in hundreds of hours of overtime free of charge.