But the Deputy Prime Minister inisted the new approach was not a U-turn but a recognition that the policy was not working as it should and needed to be adjusted. The change of tack came after an internal UK Government review this week which showed almost 60 per cent of households affected by the housing benefit changes were in arrears and that a shortage of smaller properties meant less than five per cent of tenants had been able to downsize to avoid it.
Last autumn, the LibDem leadership came under intense pressure after the annual conference voted overwhelmingly to commit the party to reviewing what activists branded a "reprehensible and evil" policy.
Danny Alexander, the Chief Secretary to the Treasury, who revealed the shift, defended the principle of the "spare room subsidy" reforms but admitted they now needed to be significantly adjusted.
He referred to how the LibDem conference had wanted a review, which reported this week, and had confirmed some of the party's concerns.
"That's the reason for the timing," he insisted. "It's off the back of the detailed evidence of some of the impacts."
The Highland MP made clear no-one should face a cut in state help if there was no suitable smaller property available and all disabled claimants should be exempt.
But Rachel Reeves for Labour was scathing, accusing the LibDem leadership of "unbelievable hypocrisy".
"The LibDems voted for the bedroom tax, there wouldn't be a bedroom tax if it wasn't for the LibDems.
"And in February when Labour tabled a bill to scrap the bedroom tax, the LibDems were nowhere to be seen," declared the Shadow Work and Pensions Secretary.
She added: "It is clear the only way to cancel the bedroom tax is to elect a Labour government next year." Meanwhile, the Tories called the LibDem move a "cynical PR stunt" and stood by the reforms.
Downing Street said there would be no change of policy.