The chancellor is set to use this week's Budget to outline new regulations to help the poor pay their fuel bills.

MPs, unions and consumer groups have called on Alistair Darling to levy a windfall tax on energy companies in this week's Budget in order to tackle fuel poverty.

This could take back some of the large profits recently recorded by energy firms at the same time as rising prices, in part due to free permits given to them under the European Emissions Trading Scheme.

Unite union general secretaries Tony Woodley and Derek Simpson said on Monday: "It is barely comprehensible that energy companies are announcing multi-billion pound profits and at the same pushing through massive price hikes.

"When we have so many people, especially pensioners, the low paid and those on benefits, in the throes of fuel poverty, it does not make sense to ordinary people."

The option of a tax remains open to ministers, but the government is thought to prefer a regulatory approach.

However after failing to agree a voluntary deal with gas and electricity suppliers over the higher costs faced by low-income customers on pre-payment meters, Darling is expected to announce he will apply laws which allow him to control prices.

Firms are thought to charge an average £225 more per year for energy bought on the meters, rather than by direct debit. Campaigners say this is contributing to the sector making £400m in 'excess' annual profits from some of the worst off in society.

The chancellor will add that talks are ongoing with the industry on a wider fuel poverty package, aimed particularly at helping the elderly with their bills.

Business secretary John Hutton was on Monday also set to announce guidance to industry regulator Ofgem to help make sure that it takes a lead in ensuring that poorer customers have the information they need to switch suppliers.