The vast majority of social housing tenants affected by the bedroom tax have no smaller properties available to them to downsize to.

Freedom of Information requests of local authorities by the Labour Party found that 96% of people hit by the government's controversial under-occupancy policy are effectively trapped in their current homes because of a countrywide lack of smaller accommodation.

The 38 local authorities that supplied complete statistics revealed that a combined total of 99,079 families are forecast to be struck by the policy in their boroughs.

However, the councils have only 3,803 one and two-bedroom social homes collectively available for their tenants to downsize into.

A further 26 councils who answered the FOI said they expected 45,669 families to be caught by the tax but didn't have any information on the amount of smaller properties available.

Last month it was revealed that Westminster City Council had managed to rehouse only 28 of 440 tenants affected by the bedroom tax in the borough.

In June councillors representing 36 councils met at a summit in Manchester to urge the government to abolish the policy.

The Department of Work Pensions (DWP) has defended the policy and claimed that despite the lack of smaller housing available, the FOI data "ignores the fact that people may move to housing in the private sector and not all tenants will not have to downsize because they could make up any shortfall through getting a job or increasing their working hours".

A DWP spokesperson said: "These reforms will save the taxpayer £1 billion over the next two years and help to ensure a better use of our housing stock when in England alone there are nearly two million households on the social housing waiting list and over a quarter of a million tenants are living in overcrowded homes."

A recent survey by the Chartered Institute of Housing (CIH) and Circle Housing Group found that two-thirds of social landlords would be unable to rehome any more than 20% of their tenants affected by the bedroom tax in the year following its introduction. 

And 96% said that despite offering cash incentives and practical help, a lack of available homes remained the biggest barrier for social housing tenants being able to move.

Abigail Davies, CIH assistant director of policy and practice, said: “These figures are sadly not surprising.  Our own research has shown that housing professionals are working hard to try to mitigate the effects of the bedroom tax on their tenants. 

"But there is only so much they can do – there are simply not enough smaller homes for all those affected to move into. The government says the aim of the bedroom tax is to save money, but if it ends up pushing more people into the private rented sector, it will end up being counter-productive. 

"Private rent tends to be much more expensive, so the more people there are living in private rented homes who also receive housing benefit, the more the housing benefit bill is going to increase.”