Iain Duncan Smith has dismissed an online petition calling on him to live on £53 a week on the grounds that he has experienced life on the breadline during two periods of unemployment.

As the petition hosted at www.change.org secured nearly 300,000 signatures, the work and pensions secretary told his local newspaper that it was a distraction because he had already lived on the equivalent of low benefits.

The petition says: "This petition calls for Iain Duncan Smith, the current Work and Pensions Secretary, to prove his claim of being able to live on £7.57 a day, or £53 a week."

Duncan Smith told the Wanstead and Woodford Guardian: "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."

Duncan Smith came under pressure after he told BBC Radio 4's Today programme on Monday that he could live on £53 after he was asked about a market trader, David Bennett, who claimed that he had to live on that amount after his housing benefit was cut. "If I had to, I would," Duncan Smith replied.

He has spoken of how he signed on the dole after leaving the Scots Guards in 1981 at the height of the recession. He experienced another period of unemployment in the late 1980s when he lost his job as marketing director of the property firm Bellwinch.

The Daily Mail reported Duncan Smith as saying: "It was a shock – absolutely awful. I felt pathetic. I remember telling my wife. We looked at each other and she said: 'God, what are we going to do for money?'"

Duncan Smith's wife, Betsy, is the daughter of the 5th Baron Cottesloe who served as lord-lieutenant of Buckinghamshire in the 1980s and 1990s. Duncan Smith and his wife, who sent their children to Eton, moved into Lord Cottesloe's 17th-century Old House in the village of Swanbourne in Buckinghamshire in 2002. His in-laws moved into smaller accommodation to make way for the Duncan Smiths and their four children.

Duncan Smith told the Daily Telegraph in 2002 that he found Swanbourne a relief after the hectic pace of Fulham, south-west London, where the family used to live. "I was brought up all over the place but I'm more at ease in the country," he said. "The side of London I like is the opera but I hate the noise, the dirt, the fumes and the grinding chaos."

George Osborne sidestepped questions about whether he could survive on £53 a week when he was asked about Duncan Smith's claim after a speech to workers at the a Morrisons supermarket distribution centre in Sittingbourne, Kent.

"I don't think it is sensible to reduce this debate to an argument about one individual's set of circumstances and the example that was given on the BBC radio," Osborne said. "We have a welfare system where actually there are lots of benefits available to people on very low incomes. There is jobseeker's allowance and income support, there is a working tax credit, there is council tax benefit, there is housing benefit. So there are a number of different benefits there.

"This debate is not about any individual. This is about creating a welfare system that rewards work, that supports people who do the right thing, that helps those that want to get on in life and has a regard for the many millions of people who work very hard and pay their taxes and expect their money to be well spent."

A friend of Duncan Smith said: "Iain is the last person to be flippant about this. He does not take lightly living on £53 a week. He was asked a specific question and he said yes he would live on £53 if he had to.

"Iain is passionate about [his welfare reforms]. He came back on to the frontbench to do this. This is a man who visited Easterhouse [estate outside Glasgow] and saw poverty first hand and felt so compelled to do something about it that he set up the Centre for Social Justice."