Iain Duncan Smith has insisted he understands the concerns of benefits claimants because he has been unemployed twice.
The work and pensions secretary said he had queued at the jobcentre and spent "day after day" sending out application letters.
And he mounted a strong defence of the tough welfare policies he has brought in since the Tories won power in 2010, including the benefits cap and universal credit.
Duncan Smith was speaking to the Centre for Social Justice, a London-based think-tank he co-founded. "I have had my own personal experience of the British welfare system, having had two periods of unemployment in my own life," he said on Tuesday.
"So I know what it's like. I've been there in the queue at the jobcentre and I've spent day after day sending out dozens of application letters hoping that one of them will get noticed."
He said his own experience made him realise that "change was needed in our welfare system".
Duncan Smith was first unemployed aged 27 when he left the army in 1981. He was later made redundant from a property company in 1992 and spent three months looking for work.
Duncan Smith said he believed work was "critical" for people's health and building up character.
He claimed that the previous Labour government had "trapped people in dependency" with a complex system of benefits – which created a "growing underclass" with no interest in going to work.
And he insisted his benefits cap – which limits the amount of money households can claim – ensured that claimants face "the same daily choices as everyone else".
He said: "That policy ... said the welfare system is not a bottomless pit of cash. It said the system was there to help if you need it, but we would not tolerate excessiveness from those who wanted to take advantage."
He also hailed plans for universal credit, which aims to merge six benefits into a single monthly payment. The project has been criticised by MPs for numerous delays and fears over mounting costs.
Duncan Smith, who was Conservative leader between 2001 and 2003, said he was fighting for "people who have been systematically let down by politicians".
"People who have been promised much but given little. Every statistic we quote represents real people, many of whom depend on the government to be a source of hope and help."
It emerged last year that his department had used made-up quotes from fictional claimants talking about how benefits sanctions had helped improve their lives.