David Cameron has unveiled a 'get tough' welfare reform package aimed at encouraging more benefits claimants into work.
The Conservative leader's proposals included a "three strikes and you're out" rule for unemployed people who turn down job offers.
Under the Tory scheme, any benefit claimant who receives a reasonable job offer - as defined by government guidelines - will be expected to accept it.
If they refuse they will lose one month's out-of-work benefits. A second refusal would cost them three months' benefits, and a third, payments for up to three years.
The rule could cost individuals more than £9,000 and couples more than £14,500 over three years.
"We cannot go on as we are with 2.6 million people on incapacity benefit, 500,000 of them are under 35," Cameron told BBC Breakfast.
"Are we really saying there are half a million people in this country under 35 who are simply too ill to work? I don't think that's right.
"I think we have got to make changes and this is a genuinely thought through and worked out package which I think will help get more people into work and help them make better lives for themselves and their families."
'Tough'
Cameron visited a jobseekers' project in London with shadow work and pensions secretary Chris Grayling on Tuesday.
The US-style "return to work" programmes being proposed by the Tories include forcing the long-term unemployed to join community work programmes if they want to carry on claiming benefits.
The party has also proposed a fresh assessment of all 2.6 million incapacity benefit claimants to check whether any are fit for work, suggesting that 200,000 could be cut from the list.
Those taken off incapacity benefit would receive the less valuable jobseekers' allowance, and would be expected to accept offers of work.
At the same time, the Conservatives say they would establish a network of "back to work" centres around the country, where claimants would be expected to spend most of the week.
Cameron told GMTV: "All the evidence shows that if you are out of work for a long time you lose touch with what it is like to have a job, to have colleagues at work, to get up in the morning, to go to work, all of those things really matter.
"So what we are saying to people who effectively are long-term unemployed is that we will help you stay in touch with the job market and with working by laying on these community work programmes.
"It has worked in Australia, it has worked in America. I think it is really important that we say in this country 'Look, we cannot go on as we are'."
'Very tough'
However Gordon Brown insisted that the government has "been very tough and is getting tougher" on encouraging benefits claimants into work.
Speaking at his regular press conference on Tuesday, the prime minister said the Tories were "in the old era".
"We recognise that where the problem in 1997 was a lack of jobs, the problem in 2007 is the lack of skills," he said.
Brown told reporters people were not getting jobs because "they don't have the skills for these jobs".
And pointing to measures which have been introduced to reduce the number of incapacity benefit claimants, he said the long-term unemployed had always been denied benefit "if they refused to accept work".
Brown said that "none of the measures" put forward by the Tories dealt with the "fundamental problem... about getting people the skills to get the jobs that are available and getting employers who are prepared to take them on".
