More than 96% of households affected by the so-called "bedroom tax" are unable to move into smaller properties, Labour has claimed.
An estimated 238,266 households have been hit by the housing benefit cut for people judged to have a spare room, according to 95 councils in England, Scotland and Wales which have provided data in response to Freedom of Information requests (FOI) from Labour.
Sixty-one local authorities were able to estimate how many one or two-bedroom council properties are vacant in their area, which totals 9,095. This has led to Labour concluding more than 96% of people have nowhere to move and Liam Byrne, shadow work and pensions secretary, to renew calls for the "bedroom tax" to be dropped immediately.
The remaining 34 councils which responded to the FOIs either said it was not possible to provide a figure for vacant council houses, had yet to provide the information or Labour stated it was "seeking clarity".
If only the 61 councils which have provided the full data are taken into account, which covers 161,214 households thought to be affected by the benefit cut, then the number of people unable to move to a one or two-bedroom council property drops slightly from 96.18% to 94.3%.
The coalition Government argues the changes will help cut the £23 billion annual bill for housing benefit, free up more living space for overcrowded families and encourage people to get jobs.
But Mr Byrne said: "The big lie behind this Government's spiteful bedroom tax is now plain for all to see. Ministers like to claim it's not a tax but the truth is more than 96% of those hit have nowhere to move to.
"This hated bedroom tax is trapping thousands of families, forcing vulnerable people to food banks and loan sharks, and there is now a serious danger is could end up costing Britain more than it saves as tenants are forced to go homeless or move into the expensive private-rented sector. David Cameron's bedroom tax is the worst possible combination of cruelty and incompetence. He should drop it and drop it now."
Labour-controlled Birmingham City Council has 13,557 households affected by the housing benefit cut but has 368 one or two-bedroom council properties available, according to the FOI results.
Labour says it has put requests into all councils and is chasing responses.