"Chronic" insecurity in the private rented sector in England has led to a fourfold increase since 2010 in the number of households forced into homelessness when tenancies end, according to new research.
Loss of a private tenancy is now the leading cause of homelessness in England, with the 16,000 households affected making up around a third of the 54,000 accepted as homeless by councils in 2014/15, the annual Homelessness Monitor by the charity Crisis and the Joseph Rowntree Foundation (JRF) found.
They warned that local authorities were "struggling to cope" with rising numbers of single homeless people, with 88% saying they often or sometimes find it difficult to help those aged 25-35 and 87% those aged 18-24.
Two-thirds of English councils reported that changes to the welfare system under the coalition government from 2010-15 had increased homelessness in their area, with the problem particularly acute in London, where 93% of authorities said benefit reforms have had a negative effect.
In all, 275,000 households needed help in 2014/15, including "homelessness prevention" and "homelessness relief" activity as well as rehousing. And placements in temporary accommodation rose "sharply" by 12%, bringing the total to 40% above 2010/11 levels.
Numbers of people rehoused out of their home area have risen to 26% of the total, compared to 11% in 2010/11.
The report found majority backing among councils for bringing the law in England in line with Wales, where help must be provided to anyone faced with the loss of their home and not just "priority" groups like families with children.
Some 56% of English councils said the change would be beneficial for homeless people, against 25% who disagreed.
Report author Professor Suzanne Fitzpatrick said: "The loss of a private tenancy is now the leading cause of homelessness in England, while recent housing and welfare changes could make it even harder for low income households to find a place to live. Faced with these developments, we have to ask, 'who will house the poorest?'"
Crisis chief executive Jon Sparkes said: "It's a critical time for homelessness in England. Councils up and down the country are struggling to help single homeless people and fear that recent welfare reforms are likely to make the problem worse.
"On top of the desperate human tragedy, this will be incredibly expensive for the public purse as local services are forced to pick up the pieces.
"Yet the Government has a unique opportunity to act. We strongly welcome its willingness to consider new ways of preventing homelessness, including options for new legislation; and as this report shows, such a move would be backed by a majority of English councils. This could represent one of the most radical changes in help for homeless people in nearly 40 years."
Julia Unwin, chief executive of the JRF, said: "A chronic lack of security in the private rented sector is putting more and more families at risk of homelessness.
"The Government's commitment to building more homes will help some to get on the housing ladder, but these figures show that the housing crisis cannot be solved unless much more is done to improve the number of safe, secure rented tenancies."
Local Government Association housing spokesman Peter Box said that supporting the homeless was "only getting tougher as the housing crisis intensifies".
Mr Box said: "Government still needs to go further in reforming the public sector and devolving responsibility for allocating public money for all public services - from social housing to the health service - down to locally-elected people, and must fully fund any new responsibilities it places on councils.
"One of the best ways to tackle homelessness is with bricks and mortar. Local authorities are desperate to keep increasing building and need to be able to keep playing a lead role in building and investing in more of the genuine affordable homes our communities desperately need and which are crucial to reducing homelessness and tackling council waiting lists."
The Department for Communities and Local Government said central funding for tackling homelessness was being increased over the next four years.
"We want to help local authorities provide advice and assistance to those at risk of homelessness which is why we have protected the homelessness prevention funding for local authorities," a spokesman said.