The former Prime Minister Sir John Major today called for a windfall tax on energy companies to help ease the pressure on needy customers.
Speaking to journalists, Sir John said the Government would have to intervene if prices continued to rise.
"It's not acceptable to me that many people are going to have to choose between keeping warm this winter and eating," he said at a Press Gallery lunch.
If intervention proved costly, he said, then he would favour a levy on the energy companies' profits.
Asked if he was making Ed Miliband's case for him, he insisted not.
He said the Labour leader's heart might be in the right place on this, but his head had "gone walkabout".
Scottish Power has increased its gas and electricity bills as rifts appear in the Coalition over green energy taxes.
David Cameron has announced a review of competition in the energy market and vowed to roll back green regulations.