Londoners aged 18-24 will be required to do 13 weeks' unpaid work as a condition of claiming their £56-a-week benefit

Young Londoners joining the dole queue will be forced to work unpaid for three months or lose their benefits under a new scheme announced by mayor of London Boris Johnson and the Department of Work and Pensions (DWP).

Funded from the European social fund, 6,000 Londoners aged 18-24 in 16 boroughs will be made to do 13 weeks' unpaid work as a condition of claiming their £56-a-week benefit if they have contributed less than six months of national insurance payments.

As well as charities, some will be made to work for businesses that provide a clear "community benefit".

The scheme is expected to be running by the end of the year and the government hopes to extend it nationally. It will bring the total number of proposed or operational mandatory work schemes to three. One, the mandatory work activity scheme, which lasts for a month, was found by the DWP to have zero effect on chances of landing a job. It also had no effect in getting people off benefits over a six-month period and led to a small increase in those claiming sickness support payments.

Described as a "joint pilot" between Johnson and the DWP, the new programme will offer "intensive help" for those with little experience of paid work, including one-to-one CV advice "to help people boost their employability in an increasingly competitive jobs market".

The DWP said the pilot "ties in directly" with the "mayor's pledge to help create 200,000 jobs over the next four years".

Writing about the announcement in the London Evening Standard, the employment minister, Chris Grayling, said it was time to look at a different approach to benefits.

"Most young people are trying very hard to find work – and we should make sure that they get immediate help to do so," he wrote. "But there are some who really are sitting at home and putting little effort into moving on in life.

"Other countries take a much tougher approach. When it comes to benefits for young people straight out of education, forget it. You don't get social security until you've worked and paid something in.

"It's time to look at a different way in Britain. A something-for-nothing culture does no one any favours."

Grayling took a swipe at the Labour party and those campaigning against "workfare". "The usual suspects will cry 'slave labour''. They always do. But they are the people who believe that young claimants have the right to sit at home playing computer games. I simply disagree."

Liz Wyatt from Boycott Workfare said: "Grayling and Johnson are clutching at straws. After seeing their last youth workfare scheme fall apart after public anger at young people being forced to work in Tescos and Holland & Barrett, they are trying to rebrand their latest efforts as being for so-called community benefit.

" But this will not fool the public who know that workfare in any guise is unacceptable.

"The something-for-nothing culture that Grayling talks about is found amongst the organisations who are receiving free forced labour not amongst our young people who receive only subsistence benefits."

Pat Carmody, from the group Right to Work, said young people had already been "knocked out" of training and education by cuts to the educational maintenance allowance and increases in tuition fees.

He described the scheme as a punishment. "Workfare has not helped people into employment," he said. "Again, it is another punishment directed at those at the bottom of society. Every single activist needs to mount a campaign to force another U-turn on such a vicious policy"

He said it was disgraceful that extra funding from Europe was going to provide businesses with free labour instead of "ensuring that people get a decent standard of living".

Johnson said: "It's no secret that work experience can be the key that opens the door to a successful career and more young Londoners need to be given the opportunity to do it. Right now, it's a tough labour market out there and we have to ensure that all young people get the skills they need to succeed and for which employers are crying out."