Nearly 200 MPs are calling on Theresa May to stand up to energy firms and introduce an energy price cap.
In a cross-party effort, lawmakers have written to both the Prime Minister and Greg Clark, the business secretary, saying that the government needs to protect households on standard variable tariffs (SVTs).
The 192 MPs have said that the energy regulator Ofgem has ignored a "stitch-up" on the part of the 'Big Six' energy firms and that the government must intervene.
The Conservatives, Labour and the Scottish National Party all pledged to introduce a price cap in their manifestos ahead of the snap General Election.
Conservative MP John Penrose said: "For decades the 'Big Six' energy companies have ripped off 17m customers. And yet Ofgem have chosen to stand idly by, leaving 15m customers on SVTs to be preyed upon.
"If Ofgem won't challenge the 'Big Six' and stand up for consumers, the government should replace it and implement the energy price cap itself."
A spokesperson for the department of business, energy and industrial strategy, said: “The government is determined to see the huge detriment suffered by loyal energy consumers addressed. The Business Secretary asked Ofgem to advise on what measures it will take to safeguard consumers and, while we await the regulator’s proposals, we remain prepared to legislate if necessary.”