
More than 80 Labour MPs have signed a petition calling for a one-off windfall tax to be imposed on energy firms who have recently recorded huge profits.
The MPs, including several ministerial aides, want the government to use the money generated to help poorer families who are struggling to pay their bills.
Pressure group Compass, which organised the petition, said it expected more MPs to sign after the summer recess.
The government says it is "looking at" all options to tackle the issue.
While a windfall tax has not been ruled out, it is understood the prime minister is looking at an alternative levy on carbon emissions.
Earlier this month, Business Secretary John Hutton said the Chancellor Alistair Darling had some "very difficult calls" to make.
But he said the UK must be wary of any "fiscal" or "regulatory" changes to the energy sector that could prompt investors to go elsewhere.
The "big three" energy firms - Shell, BP and British Gas - have recently posted substantial profits.
Shell made £4bn in the second quarter of this year, up 4.6% from 2007, while BP made £3.4bn, a rise of 6%.
Centrica, which owns British Gas, made £992m in the first half of this year, while raising prices for customers by 35%.
The government imposed a windfall tax on the profits of recently privatised utility companies in 1997.
On Sunday, a YouGov poll for The Observer newspaper of just over 2,000 people found that 67% supported a windfall tax.