Prove it! Campaigners deliver petition calling for Iain Duncan Smith to live on £53 a week to his Whitehall office

Petition with almost half a million signatures demands the Work and Pensions Secretary backs up his claim

The Work and Pensions Secretary has today accused some welfare applicants of getting their claim in early to avoid stringent new conditions, as a petition with more than 460,000 names calling on him to back up his claim that he could live on £53 a week was handed in to his office.

Iain Duncan Smith, who lives in a 16th-century Tudor mansion, made the claim last week as he announced reforms to the benefits system. The petition, the fastest-growing in the history of the Change.org website, was dismissed as a “complete stunt” by Mr Duncan Smith, who said he had experienced life “on the breadline”.

The petition was set up when David Bennett, a market trader, said the sum was all he had to live on after his housing benefit was cut. Mr Duncan Smith responded by claiming he could manage on that amount.

It asks demands that Mr Duncan Smith prove his claim by doing so for a year.

But the Work and Pensions Secretary told his local newspaper last week: “This is a complete stunt which distracts attention from the welfare reforms which are much more important and which I have been working hard to get done. I have been unemployed twice in my life so I have already done this. I know what it is like to live on the breadline.”

Shop Assistant Dominic Aversano handed over the petition, who started the petition. The 28-year-old from Twickenham, south west London, said: "I don't think Mr Duncan Smith has a choice about whether to listen to the petition because so many people have signed it.

"I think it has changed the debate around welfare cuts. I was very surprised because I didn't think we would have such a large response. I am delighted."

Security staff, seeing the group approaching, locked the doors to the building and - initially at least - refused to accept the petition.

Mr Aversano said: “That is in keeping with pretty much everything that Iain Duncan Smith has done, he has been ignoring all the people who signed the petition. And so, to ignore us when we come to the door is not really a surprise to me, it proves the point even more."

John Coventry of campaigning website Change.org, which hosted ithe petition, said: “Funnily enough, the last time we were locked out like of a building was the Chinese embassy when we were handing in hundreds of thousands of signatures to free human rights activist Liu Xiaobo about three or four months ago.”

It took various attempts and numerous calls and emails to Department staff to eventually persuade them to allow the petition through the doors.

Mr Coventry said it was the largest his organisation had ever hosted.

He said: "This has really taken the debate out of politicians' hands and put it back in the hands of the people. Social media has the power to do that now."

Mr Duncan Smith went on the offensive today, claiming people have been rushing to get disability benefits before the coalition toughens up the system.

He said a surge in applications before the personal independence payment (PIP) started coming into force today demonstrated why reform was needed.

He told the Daily Mail: “Seventy per cent of people on it have lifetime awards which means no one sees you ever again. It doesn't matter if you get better or your condition worsens - it's quite ridiculous.

“We've seen a rise in the run-up to PIP. And you know why? They know PIP has a health check. They want to get in early, get ahead of it. It's a case of 'get your claim in early'.”

He added that rigorous new health checks for claimants were “common sense”.

Both Downing Street, on behalf of David Cameron, and George Osborne have sidestepped questions on their ability to cope on such an income. But Greg Clark, the Treasury minister, admitted that any politician would find it difficult to live on £53 a week.