The funding gap for providing adult social care in the capital will amount to £907 million within five years, according to a report published by London Councils.
The report from the think-tank and lobbying group warns how local authority budget cuts coupled with the need for increased spending on adult care services over the coming years will lead to the considerable funding gap by 2018.
Councils in the capital currently spend a third of their total budgets on adult social care services, and spending is set to rise dramatically as the number of Londoners aged 65 and over increases by an estimated 50,000 over the next five years.
The report, called A Case for Sustainable Funding for Adult Social Care, also warns that by 2020 social care and waste collection could require more than 60% of all local authority funding.
The gap was estimated assuming a 5% cut in local authority budgets at the next spending review. However, if the cut was as much as 15%, this figure would rise to £1.1 billion.
The new report, supported by Ernst & Young, states that the only way to fully bridge the gap is to change the levels of funding allocated from Government or through reforming how adult social care is funded.
London Councils' executive member for adult services, councillor Ravi Govindia, said: "We want Londoners to lead fit and active lives and stay healthy well into old age, but if people do need support, affordable social care services need to be available for them."
According to Age UK, of the two million older people in England today with care-related needs, nearly 800,000 receive no support of any kind from public or private sector agencies. London Councils is now urging the Government to help tackle the problem in the capital.
Care minister Norman Lamb said: "We recognise the pressures on the adult social care system, and that is why we have allocated an additional £7.2 billion up to 2014/15.
"Additionally, we have provided extra funding to local authorities for adult social care over the next two years, which will provide an extra £100 million in 2013/14, and £200 million in 2014/15."