Youngsters on the Government's work experience scheme will be able to leave after a week without facing benefit sanctions under a change announced by ministers aimed at heading off criticism of the programme.
The move followed a meeting with scores of employers following protests by activists who complained that youngsters were being forced to work for nothing.
The Department for Work and Pensions (DWP) said sanctions would still apply for cases of gross misconduct, such as stealing or racist abuse, but those taking part in the scheme would be able to leave after a week without losing their benefits.
Employment minister Chris Grayling described it as a "change" that would help companies, insisting that opponents were "completely misguided".
He said: "Following a productive meeting with employers I am delighted that we have pledges from some of the UK's top companies to take part in the scheme.
"The likes of Airbus, Centre Parcs and HP Enterprise Services will join in Voluntary Work Experience helping our young unemployed people get their first vital step into employment.
"Despite the persistent campaign of the last two weeks we have had contact with over 200 small or medium enterprises also wanting to get involved.
"The work experience scheme remains and is totally voluntary.
"The sanction regime remains in place.
"Employers continue to have the protection with the use of sanctions for gross misconduct.
"We have used the meeting to explain how the regime applies. It has never been an issue with the programme as only 220 people have been sanctioned since it started."
The Government launched a strong defence of the scheme, announcing that hundreds of new small to medium-sized firms had expressed an interest in taking part since controversy over benefit sanctions flared recently.
Prime Minister David Cameron told the Commons: "I think the whole country wants to see young people given the opportunity that work experience provides.
"I think it is time that businesses in Britain, and from everyone in Britain, who wants to see people have work experience, stand up against the Trotskyites of the Right to Work campaign and perhaps recognise the deafening silence we have had from the party opposite."
Deputy Prime Minister Nick Clegg said of the scheme's opponents: "They are criticising a programme that is deliberately trying to help young people into work. I cannot for the life of me understand the kind of messed-up sense of priorities of people who want to prevent young people from finding opportunities to get into permanent work."
TUC general secretary Brendan Barber said: "We welcome the Government's climbdown on the use of sanctions in work experience.
"Of course proper work experience can be useful and helpful for many young people, but it needs to be designed to help the young person, not provide free labour for employers or displace paid staff.
"Making absolutely clear that it is voluntary at all times will help safeguard against abuse."
Katja Hall, the CBI's chief policy director, said: "It's good to hear that many more employers are signing up to give young people a chance to get experience of work.
"Gaining hands-on experience of the workplace is vital to giving young jobseekers a foot in the door, and it can make such a difference when they are applying for interviews. The advantage of this scheme is that they gain work experience while remaining on benefits."
Mark Dunk from the Right to Work campaign, said: "The dropping of sanctions for the work experience scam is one battle won but the wider fight goes on.
"Forced unpaid work still continues in the form of the mandatory work activity and community activity programme. We demand that the Government immediately drops not just one of its forced labour schemes, all of them.
"There should not be any young person anywhere forced to work for no pay.
"Everyone on any training scheme should receive minimum wage or above."
Protest groups said they would press ahead with demonstrations against the scheme across the country on Saturday.
Shadow work and pensions secretary Liam Byrne said: "The Government seem to be making this up as they go along, and frankly this country's youth unemployment emergency demands far more.
"Ministers appear to be lurching from one muddle to another while more and more jobs are lost and unemployment rises.
"Work experience is incredibly valuable but somehow this Government have botched it so badly that they have lost the good will of businesses across the country."