Iain Duncan Smith has been criticised by the UK’s statistics watchdog for allegedly misusing figures to argue that his benefits cap is pushing people into work.

The work and pensions secretary and Chingford MP previously said the cap was producing “the desired impact” as 8,000 people who would have been affected by the cap had now got jobs.

But the UK Statistics Authority said this statement was not reflected in official figures.

Mr Duncan Smith is rolling out a cap on the total number of benefits people of working age are eligible for across the UK, and told the Daily Mail in an interview that 8,000 people “decided to act” after his department wrote to them to advise their benefits were to be cut.

The authority said the official figures do demonstrate that 8,000 people who could potentially have been hit by the cap had got jobs.

But the authority claimed the figures had come with a warning that they were “not intended to show the additional numbers entering work as a direct result of the contact [from the DWP]”.

The authority further points out that although the number of households expected to be affected had fallen from 56,000 to 40,000 that was due to policy changes rather than any “behavioural change” in those receiving benefits.

However, the article quotes Mr Duncan Smith saying: "The benefit cap sets a strong incentive for people to move into work and even before the cap comes in we are seeing thousands of people seeking help and moving off benefits."

“Already we've seen 8,000 people who would have been affected by the cap move into jobs. This clearly demonstrates that the cap is having the desired impact."

UK Statistics Authority chairman Andrew Dilnot has written an open letter to the secretary of state to say the figures, released in April, do not fully comply with UK codes of practices on statistical releases.

He raised concerns around information on the methodology and sourcing of the figures, and the possible sharing of the data with media outlets in advance of their release.

A petition has now been started on www.change.org which has attracted more than 50,000 signatures calling on MPs to hold Duncan Smith’s use of statistics to account.

The DWP said responses of staff and claimants supported Mr Duncan Smith's public statement.

A spokesman added: "The secretary of state has long held the position that the benefit cap would have an impact on the behaviour of claimants.

"As the minister for employment made clear in a recent interview, DWP staff and claimants are telling us the cap is impacting behaviour and leading to those affected finally entering the world of work.

"It's important to remember that all those potentially impacted by the cap have been contacted by DWP staff who work with the unemployed day in, day out."