Politicians from all parties have been urged to work together to find a way to overhaul the "failing" social care system in England.
Cross-party talks about the care given to the elderly and disabled failed in 2010 but will start again this month.
In an open letter, charities, faith-based groups and senior figures in the NHS and local government say the opportunity must not be missed.
A government statement said social care reform was an "urgent priority".
Care services minister Paul Burstow, a Lib Dem, said plans to change the system would be published in the spring.
But before that politicians are seeking to achieve cross-party consensus on the best way forward.
Mr Burstow, the Health Secretary Andrew Lansley, and shadow health secretary Andy Burnham are expected to hold the first in a series of meetings within the next few weeks.
In the letter sent to the prime minister and published in the Daily Telegraph, 72 signatories, including leading figures from charities such as Carers UK and Age UK, as well as peers, academics and members of the British Medical Association and NHS Confederation, have suggested they should not squander the opportunity.
The letter said: "We should celebrate the fact that we are all living longer lives, particularly disabled people and those with long-term conditions.
"But the unavoidable challenge we face is how to support the increasing number of people who need care.
"It is currently a challenge which we are failing to meet - resulting in terrible examples of abuse and neglect in parts of the care system.
"This comes at huge cost to the dignity and independence of older and disabled people, but also to our society, family life and the economy."
The letter went on to say people were being left "lonely, isolated and at risk" because of the problems with the current system.
It cited research produced by Age UK which suggested that of the 2m people with care needs, 800,000 were not getting any support because councils had started restricting access to services.
In a separate interview with the BBC, Councillor David Rogers of the Local Government Association said councils, which are in control of running the means-tested system, are united in their view of the need for change.
He said: "There is no doubt about the urgency and need for reform. Without exception, across local government all parties are in agreement. National politicians must try to come up with something."
In response to the Telegraph letter, Mr Burstow said: "The coalition agrees that the reform of social care - and the dignity and independence of older and disabled people - are an urgent priority".
He said the government had put an extra £7.2bn in the budget for social care over the course of this parliament and on Monday had announced an extra £150m this year for social care to help people be supported to get care at home and relieve pressures on the NHS.
"We'll bring forward a white paper and a progress report on funding reform in the spring setting out our plans," he added.
Attempts to reform the system collapsed before the last election after cross-party talks failed.
Labour accused the Tories of dirty tricks after they launched a campaign suggesting Mr Burnham, who was then health secretary, wanted to introduce a death tax to pay for changes to the system.
Once again, the way any new system is paid for is expected to be the most controversial and difficult element of the discussions.
The government refused to comment on the upcoming talks, but Mr Burstow said ministers saw reform of social care as an "urgent priority".
Mr Burnham said: "This is an extremely important issue that transcends party politics and we look forward to playing our part in any discussions."