Iain Duncan Smith's flagship cap on benefits has failed to help most benefit claimants into work, analysis by his own department suggests.
The work and pensions secretary has insisted that his £26,000-a-year benefits cap would drive people to make the "positive move into work".
However, the respected Institute for Fiscal Studies issued a damning verdict of the cap, which is set at £500 a week for couples and families and £350 for singles.
Using the Department for Work and Pensions' own figures, the IFS conclude: "What the quantitative analysis does tell us is that the large majority of affected claimants responded neither by moving into work nor by moving house."
Duncan Smith has defended the benefits cap, which has affected over 50,000 households, insisting: "We know that the benefit cap has had a real impact in changing attitudes and behaviours."
He has cited research by the DWP which suggests that 12,000 households are no longer affected by the benefit cap because they have found work or are no longer claiming housing benefit at all.
The opposition poured cold water on Duncan Smith's claims, warning that people are not necessarily moving into work due to his benefits cap.
Labour's Sheila Gilmore, a member of the Commons Work and Pensions committee, told the Huffington Post UK: "As in all developed economies, people in the UK regularly move into and out of work, so it’s hard for Iain Duncan Smith to claim his benefits cap is solely responsible for individuals taking up one job or another.’
"And even if you do buy the Tories’ line on the benefits cap, any savings are well outweighed by spending increases elsewhere because they have failed to tackle the root causes of high social security spending. Labour would do so by boosting the minimum wage, building more houses and helping more people with disabilities into work."