The 'ageing tax' is a central plank of a consultation launched by the Prime Minister on Monday in the face of a growing crisis over who should meet the costs for the care of the elderly.

Under proposal put forward by the government, the 'ageing tax' could run alongside the existing National Insurance levy.

The Labour government would prepare a green paper early in 2009 on ways to provide adequate non-medical care for the elderly, but legislation before 2010 is unlikely.

Media reports quoted the Prime Minister Brown as saying that he wanted to free people from the fear that they would be forced to sell their homes to pay for care, and called the current means-testing system unfair for those who had saved.

Over the next 20 years the number of people over 85 in England will double and the number over 100 will quadruple. Nearly 2 million more people will need social care support including help with dressing, washing, shopping and eating, The Guardian daily of Britain said.

In 1999 the British government rejected a proposal for free care for all made by a royal commission that Blair himself had set up. In 2006 it also shelved the recommendations of a second major review, chaired by Sir Derek Wanless.

Because of rising property prices, few homeowners now qualify for help. Charities estimate that 70,000 people a year are now forced to sell their homes to pay for residential care, which costs an average of 450 pounds a week.