Gordon Brown is facing growing demands to help hard-pressed families by imposing a windfall tax on energy firms.
More than 70 Labour MPs have signed a petition urging the Prime Minister to claw back some of the huge profits made by companies.
One Government member has publicly threatened to quit unless proposals for a significant one-off levy are brought forward this autumn.
Rob Marris, parliamentary aide to Northern Ireland Secretary Shaun Woodward, told The Times: "I'm sure there will be a change of policy this Autumn.
"What the detail is of that change will determine the level of my enthusiasm for remaining."
However, Chancellor Alistair Darling is believed to be resisting the idea of a windfall tax. There are fears that companies would merely pass on the cost to customers who have already been hit hard by soaring fuel prices. The move could also hit investment in infrastructure and renewable energy sources.
The petition, organised by left-wing Labour group Compass, has been signed by several Government members, including Stephen Pound - aide to welfare minister Stephen Timms.
Backbencher Clive Betts said there was "overwhelming" support for a one-off tax among his parliamentary colleagues.
He told the BBC Radio 4 Today programme that companies were looking at more than 30% increases in their profits, adding: "They are simply going to make much more money for doing absolutely nothing.
"I think it's reasonable for people to say 'Why should the wages and salaries and bonuses of the executives of these companies, which will be linked to their profits and their share prices, go up astronomically while the ordinary person in the street is seeing their wages go up by 2%... and their energy bills going up by 30%?'"
