More than 400,000 vulnerable people could lose vital support under projected cuts to the Supporting People programme, the National Housing Federation warned.
The umbrella group said this would be the consequence of 40% cuts from 2011-15 in the programme, which funds housing support services for learning disabled people, those with mental health problems, older people and those fleeing domestic violence.
The Department for Communities and Local Government, which funds the programme, has been asked to model cuts in its budget of 40% over this period although the precise level of reductions will not be known until the spending review reports in October.
Earlier this week, the NHF, Homeless Link and housing agency Sitra had issued warnings about cuts to SP in their submission to the spending review.
Big cuts have already been made or proposed to Supporting People at councils including the Isle of Wight and East Sussex.
This is despite evidence that the programme, costing £1.64bn this year, generates annual savings of £3.4bn for the public purse by intervening early to avoid people needing more acute services.
NHF chief executive David Orr said: "If the Supporting People budget is substantially cut it will lead to many vulnerable people losing the support they depend on, with the result that they will no longer be able to lead self-sufficient lives and will increasingly have to rely on acute health and other services.
"The government has repeatedly said that it wants to protect the vulnerable and yet these cuts would hurt many of the most susceptible people in society. It would also lead to increased demands on the health service, social services and the criminal justice system - and have profound social repercussions."
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