The Government has been criticised over failing to do enough to tackle the sharp rise in homelessness over the last six years that has been partly fuelled by its own welfare reforms, according to a report by the public spending watchdog.

All forms of homelessness have increased "significantly" and are costing more than £1 billion a year to deal with, it found.

There has been a 60% rise in the number of homeless families, which includes 120,540 children, the National Audit Office said.

The NAO said a snapshot overnight count last autumn recorded 4,134 rough sleepers, an increase of 134% since the Conservatives took power.

The report added that ending of private sector tenancies has now become the main cause of homelessness in England, rather than changes in personal circumstances such as relationship breakdowns.

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Rents have increased at the same time as household incomes from benefits have been cut, it said.

Local housing allowance reforms are "likely to have contributed" to making tenancies for claimants less affordable and "are an element of the increase in homelessness", according to the report.

The report criticised the Department for Communities and Local Government's "light touch" approach which has continued despite the obvious growing problem, the NAO said.

Auditor General Sir Amyas Morse said: "It is difficult to understand why the department persisted with its light touch approach in the face of such a visibly growing problem".

The report said rents have increased at the same time as household incomes from benefits have been cut. Credit: PA

The Department for Work and Pensions has been unable to assess the impact that changes to local housing allowance have had on homelessness, the report said.

"It appears likely that the decrease in affordability of properties in the private rented sector, of which welfare reforms such as the capping of local housing allowance are an element, have driven this increase in homelessness," the report states.

NAO analysis found private sector rents in London have gone up by 24% since 2010 which is eight times the average rise in earnings.

Across England costs have gone up by three times as much wages, except in the north and East Midlands.

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Most of the £1.1bn councils spent on homelessness in 2015/6 went on temporary accommodation.

Over the same period spending on other services, such as prevention, support and administration, fell by 9% down from £334 million to £303 million.

It also found that local authorities in London have been buying properties outside of the capital to house homeless families.

Labour's Meg Hillier, who chairs the Public Accounts Committee, said: "It is a national scandal that more and more people are made homeless every year.

"This reports illustrates the very real human cost of the government's failure to ensure people have access to affordable housing.

A Government spokesman said tackling homelessness is a "complex issue" with no single solution.

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"We're investing £550 million to 2020 to address the issue and implementing the most ambitious legislative reform in decades, the Homelessness Reduction Act.

"There's more to do to make sure people always have a roof over their head and ministers will set out further plans shortly, including delivering on our commitment to eliminate rough sleeping entirely," said the spokesperson.

Local Government Association housing spokesman Martin Tett said: "Rising homelessness is a huge challenge for councils, which are having to house the equivalent of an extra secondary school's worth of homeless children in temporary accommodation every month.

"The net cost to councils of doing this has tripled in the last three years, as they plug the gap between rising rents and frozen housing benefit.

"Councils are working hard to tackle homelessness and are focusing on preventing it happening. We now need the Government to support this local effort, by allowing councils to invest in building genuinely affordable homes and providing the support and resources they need to help prevent people becoming homeless in the first place."

The chief executive of homelessness charity Shelter, Polly Neate, said: "The NAO has found what Shelter sees every day - that for many families our housing market is a daily nightmare of rising costs and falling benefits which is leading to nothing less than a national crisis.

"That's why we are calling on the Government to act now, in this year's Budget, to end the freeze on housing benefit and to commit to building decent homes at affordable rents. Without this action this is a crisis which will only get worse."