Figures released by the Department for Education (DfE) show that 24.95 per cent (1,370) of the 5,490 young people in foster care who turned 18 since Staying Put legislation was introduced remained with their foster carers.
Fostering experts say a lack of financial support and inconsistent help for carers is hindering take up of Staying Put.
Under the initiative, which was made law through the Children and Families Act 2014, councils have a duty to support looked-after children who want to remain with their foster carer until they are 21.
Kevin Williams, chief executive of The Fostering Network, said: “Our concern is that local authorities are not being supported adequately with the implementation of Staying Put.
“Anecdotally we are hearing of far too many instances where foster carers are not being supported sufficiently in caring for a young person post-17 and so the placement is forced to break down.”
“Not every young person wishes to stay in their fostering placement after they turn 18, but for those who do we believe that they, and their foster carers, should be supported practically and financially to make it happen.”
Williams has called on the government to ensure that adequate financial support is available so that foster carers “aren’t out of pocket for keeping their door open for a young person on their journey into adulthood.”
David Simmonds, deputy chair of the Local Government Association, said councils are "absolutely committed" to ensuring that as many young people as possible can stay with their foster families if they choose to, but added that the arrangements have to be sufficiently resourced.
“Councils remain concerned that the cost to councils of keeping children with foster parents until they are 21 has been significantly underestimated by government," he said.
"Councils had already faced an estimated funding shortfall of £13m in the first six months of the scheme and this is expected to have increased significantly since then.
“In the light of 40 per cent reductions to their budgets over the last parliament, and a growing demand for children’s services, councils are having to make some difficult decisions about the services they can continue to offer.
"Any further unfunded pressures could threaten to impact on our ability to keep children safe and happy.”
News of low levels of take-up come after a National Children’s Bureau report published in June found that a lack of financial support was preventing more looked-after children remaining with their foster carer under Staying Put arrangements.
Two thirds of carers and children’s professionals told the NCB that low funding levels were preventing carers from taking part in Staying Put.
The DfE has allocated £42.4m to councils to cover the cost for the first three years of Staying Put, with £14m allocated for 2015/16 and £21m in 2016/17.
Children’s minister Edward Timpson said: “Making the journey into adulthood can be daunting, bringing new pressures, whether that’s finding a first job or starting an apprenticeship, college or university.
“Supporting young people to remain with their family until they’re ready to leave home will give them the same opportunities as their friends, and set them on the right path to the bright future they so clearly deserve.”
