The allowance paid to help people pay rent for private housing is failing to cover their costs, according to new analysis.
The Chartered Institute of Housing (CIH) and Shelter say fewer than one in five private rental properties in England are 'viable' within the current Local Housing Allowance rates.
They say the average renter now faces a £151 a month shortfall and the figure is likely to rise.
The Government says it recognise the pressures of rising rents and has maintained a £1bn boost to Local Housing Allowance rates which provide more than a million claimants with an extra £600 a year on average, and expects to spend over £30bn on housing support this year.
Charlie Berry, policy officer at Shelter, said: 'These huge shortfalls leave private renters at high risk of going into rent arrears and push families towards homelessness.
'With fewer and fewer affordable private rentals for people on housing benefit and a severe shortage of social housing, we are sadly left with a homelessness crisis.
'There are now more than 101,000 homeless households living in temporary accommodation, the highest number for almost 20 years.
'The evidence is clear: the Government must end the damaging freeze to local housing allowance which is leaving low-income families with nowhere they can afford to call home.'
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