Iain Duncan Smith dismissed demands for him to try to make ends meet on £53 a week as a "complete stunt" and insisted he had experienced life "on the breadline" as ministers confronted their critics over wider-ranging cuts to benefits.

The Work and Pensions Secretary was backed by the Chancellor George Osborne in arguing that welfare reforms were essential to helping recipients back into work and tackling Britain's previously burgeoning benefits bill. They believe the majority of voters - particularly lower-paid workers - back the Coalition's moves to trim welfare spending.

By last night almost 300,000 people had signed an online petition challenging Mr Duncan Smith to survive on £53 a week, or £7.57 a day, after he insisted he could "if I had to".

Download the new Independent Premium app Sharing the full story, not just the headlines

It was set up when David Bennett, a market trader, told BBC Radio 4 that the sum was all he had to live on after his housing benefit was cut - and Mr Duncan Smith responded by claiming he could manage on that amount.

But the Work and Pensions Secretary told his local newspaper: "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."

Both Downing Street, on behalf of David Cameron, and Mr Osborne 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.

"I think it's an incredible struggle to do that and I think any MP, anyone earning the comfortable wage that an MP has would certainly struggle.

"I think the context is this - we're all having to tighten our belts…right across the board there are difficult choices to be made, it is an incredibly difficult situation," he told BBC Radio 5Live.

The row began as cuts to benefits came into force this week. They include reductions of up to 25 per cent in housing benefit payments if recipients are deemed to have spare rooms - the so-called "bedroom tax" - and below-inflation increases in benefit rates.

Inside Politics newsletter The latest news on Brexit, politics and beyond direct to your inbox Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive updates on politics every morning by email Update newsletter preferences

Disability living allowance is being replaced by the personal independence payment, while trials are due to begin in four London boroughs of a £500-a-week cap on household benefits. The first pilot of the new Universal Credit system also begins this month.

In a speech in Kent yesterday, Mr Osborne said the welfare system was "fundamentally broken" and hit out at critics of the Government's plans, who include church leaders and charities, accusing them of talking "ill-informed rubbish".

Arguing that ministers were simply trying to restore "some common sense and control on costs" on spending, he said that by the year 2010 an "unaffordable" one pound in seven paid in tax was being spent on working age benefits.

The Chancellor said the changes were "all about making sure that we use every penny we can to back hard working people who want to get on in life".

He also mounted a fierce defence of his decision to lower the top rate of tax from 50p to 45p, asserting that it was "essential" to help get the economy growing. The reduction comes into effect on Saturday.

Acknowledging the move was "controversial", he said: "In a modern global economy, where people can move anywhere in the world, we cannot have a top rate of tax that discourages people from living here, setting up businesses here, investing here, creating jobs here."

The Chancellor cited France, where the Government is planning to "whack up their top rate of tax" and job creation rates were falling.

"The opposite is happening here because we are welcoming entrepreneurs and wealth creators - and the jobs they bring with them," he said.

He said the 50p rate - brought by Labour weeks before the election in 2010 was a "con" as amounts of tax collected fell.

"We got the worst of both worlds: a tax rate that discouraged enterprise and didn't raise more money from the rich. You can't pay down the deficit with that."

Mr Duncan Smith came under fresh pressure last night over his scheme to replace as string of benefits and tax credits with Universal Credit, which is due to be rolled out from October.

MPs on the Commons Communities and Local Government select committee raised fears that the overhaul will leave the benefits system more vulnerable to fraud.

It highlighted concerns that the computer system underpinning Universal Credit will have trouble distinguishing between genuine and bogus claims.

It said in a report published today that it is "worrying that the system still seems to be at the development stage".

FIRST TASTE OF LIFE OF THE DOLE

Iain Duncan Smith’s first taste of life on the dole came at the age of 27 after he left the Army, where he had been a Captain in the Scots Guards.

He claimed unemployment benefit for several months before joining GEC-Marconi in 1981. He joined the Conservative Party the same year and stood in the general election six years later.

After seven years with GEC, Mr Duncan Smith moved to a property company as its marketing director, but was made redundant after just six months when the housing market crashed.

By now he was married to his wife Betsy, who is a baron’s daughter, with a child and a second on the way.

He once recalled: “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?’.”

During his second spell out of work, he applied unsuccessfully for several jobs before joining the military publishers Jane’s Information Group as its sales and marketing director in 1989. He eventually was promoted to the company’s operations board.

Three years later he succeeded fellow right winger Norman Tebbit as the MP for Chingford – and a political career was underway that led him to his party’s leadership and David Cameron’s Cabinet.