NICK Clegg is under pressure to axe the 'bedroom tax' immediately - instead of after the next election - after a surprise Liberal Democrat U-turn on the controversy.
Labour vowed to force a Commons vote to reverse the painful housing benefit cuts, which have forced hundreds of Southampton families into arrears.
The showdown risks further embarrassment for the Lib Dems, who must vote against their Coalition partners - or face Labour taunts that they are allowing the bedroom tax to survive.
On Wednesday, Mr Clegg said he now wanted to scrap the measure for tenants unable to downsize to smaller homes - the vast majority - admitting it “wasn't working”.
But the Conservatives insisted there would be no changes, which means benefit cuts of 14 per cent (for one extra bedroom) and 25 per cent (where there are two) will continue, in social housing.
Eastleigh Lib Dem MP Mike Thornton - a fierce critic of the bedroom tax - welcomed the U-turn, saying: “I'm delighted the Liberal Democrats have listened to the evidence and are fighting for a fairer system.
“The changes were brought in with good intentions - but it is clear that they are not working and vulnerable people are being unfairly penalised by the changes.
“When people are having to cut back on household essentials, despite the help offered through discretionary housing payments, it shows why things need to be looked at again.”
However, Mr Thornton declined to say whether he would like to see the bedroom tax axed in its current form as soon as a vote in September.
Earlier this year, it was revealed that less than one per cent of Southampton tenants hit by the bedroom tax had moved to a smaller home - just 13 of 1,444 households in the city.
In addition, 243 tenants had been plunged into arrears, an apparent insight into the hardship the measure has caused.
The Lib Dems explained the U-turn on the grounds that just 4.5 per cent of tenants nationwide have been able to 'downsize' in the first six months of the policy.
However, ministers admitted they only expected around six per cent to move every year - suggesting that, despite Mr Clegg's admission, the policy may be working better than predicted.
Labour - which accused Mr Clegg of “breathtaking hypocrisy”, after he repeatedly supported the bedroom tax - said after the election was too late.
Rachel Reeves, the party's work and pension spokeswoman, said: “Labour will look to call a vote in parliament. The Lib Dems could cancel this cruel policy now by voting with Labour.”