The Health Foundation, The King’s Fund and the Nuffield Trust said this gap would arise from a combination of funding cuts and rising demand.
Despite pressures on the NHS, boosting social care’s resources should be the government’s “most urgent priority”, they said.
Increases in social care funding are planned for later this Parliament through the Better Care Fund and the charities said these should be brought forward to next year.
Thousands more older and disabled people would otherwise be denied access to necessary care, “with severe consequences for the NHS”, they said.
According to the charities, there has been a 9% cut in real terms in social care spending by local authorities between 2009-10 and 2014-15, and 400,000 fewer people now access these services.
King's Fund assistant director for policy Richard Humphries said: “Cuts to social care funding are leaving older and disabled people reliant on an increasingly threadbare local authority safety net. For many, the care they get is based not on what they need but on what they can afford and where they live.
“More people are left stranded in hospital. This government has committed to creating a country which works for everyone, and they now need to match this with action by using the Autumn Statement to address the critical state of social care.”
Meanwhile, a County Councils Network (CCN) survey has warned that just 12% of adult social care directors think their budgets are manageable.
It also urged chancellor Philip Hammond to bring forward at least £700m of the BCF to 2017-18 to meet pressures from the new National Living Wage, rising care costs, demographic growth and insufficient funding.
CCN’s survey for a report, Delivering Adult Social Care in Challenging Times, showed 88% of directors felt their budgets were either “severe” or “critical”, and only 12% rated them “manageable”.
The 2% council tax precept introduced to support social care would cover only the extra expense of the living wage, directors said.
Some counties would struggle as a result to deliver a balanced budget before the end of this Parliament, the network warned.
Directors were also dubious about the ability of the NHS’s sustainability and transformation plans to deliver savings through integrated health and social care because of conflicting targets and misaligned settlements between the two services.
Suffolk County Council’s Conservative leader Colin Noble, the CCN’s spokesman for health and social care, said the likelihood of counties being unable to balance their budgets “should not be mistaken as financial mismanagement”.
He added: “County authorities are contending with an impossible situation of seeing budgets reduce at a quicker pace than other councils, while coping with the biggest and fastest growing elderly po
