Soaring energy prices could leave more than six million households struggling to pay their fuel bills by Christmas - the so-called fuel poverty trap - leaving in tatters government promises to eradicate the problem for the vulnerable by 2010.

Britain's six big power companies are preparing for a fresh round of price rises of up to 40 per cent, which could start as early as next month. That would drive average dual-fuel bills to £1,467 by the end of the year, up from £1,048.

National Energy Action (NEA), the campaign group, gave warning that such an increase would drive an additional 1.6 million households into fuel poverty - defined as having to spend 10 per cent or more of household income on electricity and gas. Another 500,000 entered fuel poverty earlier this year when power companies put up prices by about 15 per cent.

It would bring the number of households in fuel poverty to more than six million, or a quarter of the total. In its 1997 manifesto, the Labour Party said that one of its key priorities was to eradicate fuel poverty for vulnerable households by 2010 and altogether by 2016. Campaigners said yesterday that the Government had failed. The number of fuel poor has more than doubled since 2003, when it stood at about two million households, and could treble by the end of the year.

A spokesman for NEA said: “We are back to square one. All the progress the Government has made has been erased. It's really an unprecedented situation.”

Gordon Lishman, director-general of Age Concern, said: “Many pensioners will be horrified to hear that energy bills could rise by a further 40percent this year, potentially pushing a further 750,000 [of them] into fuel poverty. There can be no doubt that radical measures are needed to bring the Government's fuel poverty targets back within reach.

“The Government must urgently look at ways to fund measures to reduce fuel poverty, including using the extra VAT revenue gained from increased energy bills to help those struggling the most.”

The dramatic rise in gas and electricity bills, driven by a near-trebling in wholesale gas prices over the past year, has led to fresh pressure on the Government to force power companies to do more to tackle the problem.

Nick Clegg, the Liberal Democrat leader, this week called on the Prime Minister to force power companies to devote some of the £9 billion in subsidies that they will receive from the European Union's emissions trading scheme to the fuel poor. “How can it be fair to subsidise large energy companies when ordinary families cannot pay their fuel bills?” he asked.

Gordon Brown responded by saying that the Government had increased its winter fuel payment for pensioners and has negotiated an agreement with utilities to provide up to £150 million a year to help low-income families.

“We are determined to do everything that we can to reduce fuel poverty in this country,” Mr Brown said. “We are in a very difficult situation in which oil prices have trebled, and we are determined to do everything that we can to help the vulnerable families of this country.”

NEA said that it would support any move designed to increase funding for the fuel poor, including diverting EU subsidies.

On Tuesday, a parliamentary select committee will question the big six suppliers about their expectations of future price rises and what they are doing in terms of social tariffs.

Money Central: 10 tips to beat the energy crunch

Growing gloom

Number of UK households in fuel poverty

1998 4.75 million
2001 2.5 million
2002 2.2 million
2003 2 million
2004 2 million
2005 2.5 million
2006 3.5 million
2007 3.9 million
2008 4.5 million
2009 6 million?

Fuel poverty is defined as having to spend 10 per cent or more of household income on electricity and gas

Times Recommends

• House prices falling fastest in 18 years
• Britain 'faces full-year fall in GDP'
• Savills millionaire clients feel property crunch