Sector leaders and qualified social workers have welcomed proposals to allow the NHS and local authorities to co-operate on delivering adult care, but have expressed doubt over the target to release £4 billion in savings generated from joint working.

If Labour win the election, they want the two bodies to join forces to help release resources for frontline services. The government wants to find an extra £4 billion in resources from 2014. This means the NHS would be required to spend £1.8 billion on delivering social care in people's homes.

This contradicts a report last year by the Audit Commission which found that already existing joint funding arrangements between local authorities and trusts had made little difference to outcomes.

"We now need to look at this as one system, health and social care operating together, working in much closer partnership and more integrated across the country," said health secretary Andy Burnham.

Concerns over the feasibility of the £4 billion target have been raised. Richard Humphries, who is a senior fellow at think-tank the King's Fund, said the paper has made a helpful contribution by outlining that integrated outcomes were a clear objective, adding that it "stretched credulity" by stating that £4 billion was achievable.

In the report, the government said it wouldn't impose organisational restructuring, but would remain firm about the need for health and social care services to be aligned through legislation in the next parliament.

Jo Webber, deputy policy director at the NHS Confederation, said this would have little impact because trusts were already used to working with partners. She believes that changes at central government and regulatory level would best encourage integration.