By Nick Triggle
Health reporter, BBC News
Social care is currently means-tested
Pressure is growing on the government to clarify its position over the so-called "death tax" after social care chiefs and charities backed the levy.
Ministers in England are considering introducing a compulsory fee, possibly up to £20,000, to pay for social care.
The plan has been attacked by the Tories, but the Association of Directors of Adult Social Services (ADASS) said it supported the idea.
The government said it would be making an announcement soon.
John Jackson, from ADASS, which represents social service chiefs working for councils, said extra funding was "much needed".
But he dismissed the idea of having a voluntary scheme - one of the other proposals being considered.
"The problem with any voluntary insurance is that people will not think they need it and so will not take it up.
"Without getting enough people signing up the idea stops being viable. If you have a compulsory scheme, you would ensure there is enough funding to run the service in the future."
His call for a levy was supported by Counsel and Care, a charity for elderly people.
Stephen Burke, chief executive of the charity, said: "With our ageing population, the care funding gap will continue to grow without radical reform and proper funding."
The compulsory levy has been dubbed a death tax by the Tories because while it is due on retirement the proposal allows for it to be taken from the estate of a person after death.
It was one of a number of options put forward in a green paper by Health Secretary Andy Burnham last summer to replace the means-tested system currently in place.
Prime Minister Gordon Brown and Conservative leader David Cameron clashed in the House of Commons on Wednesday over the plans and the issue of social care funding now looks like it will be a key battleground during the election campaign.
The Tories have already produced a controversial poster criticising the possibility of a compulsory charge, showing a gravestone with the words "R.I.P. OFF"
Councils say they are increasingly struggling to provide support in people's homes, while thousands of people have been forced to sell their family homes to pay for residential care.
The Conservatives have put forward a plan for an optional £8,000 fee so elderly people can avoid paying for residential care.
The party has been more vague about what it wants to do over the care people receive in their own home for washing, eating and dressing.
It said it is looking to draw up plans to support people through home modifications and technology that would leave them less reliant on social services.
In contrast, the government put forward three proposals in a green paper last summer covering both care homes and help in the home.
As well as the compulsory fee, it included a voluntary insurance scheme and a partnership model whereby the state provided a basic level of support which could be topped up by individuals.
A Department of Health spokeswoman said a decision would be made soon.
She added: "It is premature to start second-guessing the blueprint we will shortly set out."