Government back-to-work schemes criticised as "forced labour" have been ruled lawful by the high court.

A judge rejected the jobless graduate Cait Reilly's claim that a scheme requiring her to work for free at a Poundland discount store breached human rights laws banning slavery.

Mr Justice Foskett, sitting at the high court in London, said that "characterising such a scheme as involving or being analogous to 'slavery' or 'forced labour' seems to me to be a long way from contemporary thinking".

Reilly, 23, from Birmingham, and the 40-year-old unemployed HGV driver Jamieson Wilson, from Nottingham, both claimed the unpaid schemes they were on violated article 4 of the European convention on human rights, which prohibits forced labour and slavery.

The judge said both Reilly and Wilson were each entitled to a declaration that there had been breaches of the 2011 jobseeker's allowance regulations in their cases.

Mistakes had been made in notifying Reilly about the requirements of the Work Academy Scheme so that she did not appreciate the scheme was not mandatory. Wilson had been given inadequate notice about the Community Action Programme.

But the judge ruled neither scheme was contrary to article 4, and the errors made did not invalidate the 2011 jobseeker's allowance regulations.

The ruling will come as a relief to the government. Had it lost the legal challenge, all back-to-work schemes might have been invalid.

The judge criticised the Department for Work and Pensions (DWP) over the lack of clarity of the letters that warn claimants of a potential loss of benefits if they fail to participate in the schemes without good reason, and called for improved clarity.

The DWP said it had revised its standard letters, but nevertheless intended to appeal over that part of the ruling.

The judge said: "Whether the problems in Miss Reilly's case and Mr Wilson's case were 'merely teething problems' remains to be seen.

"The issues raised in their respective cases were properly raised even though the principal contentions advanced have been rejected."

Rejecting the main slave labour allegations, the judge said both the schemes under challenge "are a very long way removed from the kind of colonial exploitation of labour that led to the formulation of Article 4.

"The [human rights] convention is, of course, a living instrument, capable of development to meet modern conditions, and views may reasonably differ about the merits of a scheme that requires individuals to 'work for their benefits' as a means of assisting them back into the workplace."

A DWP spokeswoman said: "We are delighted, although not surprised, that the judge agrees our schemes are not forced labour.

"Comparing our initiatives to slave labour is not only ridiculous but insulting to people around the world facing real oppression.

"Thousands of young people across the country are taking part in our schemes and gaining the vital skills and experience needed to help them enter the world of work – it is making a real difference to people's lives.

"Those who oppose this process are actually opposed to hard work and they are harming the life chances of unemployed young people who are trying to get on."

Announcing that there would be an appeal over the warning letters about sanctions, the spokesman said: "We do not believe there is anything wrong with the original letters and we will appeal this aspect of the judgment, but in the meantime we have revised our standard letters."

The law firm Public Interest Lawyers (PIL), who acted for Reilly and Wilson, said the issuing of flawed warning letters meant that "tens of thousands of people stripped of their benefits must now be entitled to reimbursement by the DWP".

The PIL spokeswoman Tessa Gregory said: "As of January 2012, over 22,000 people had been stripped of their benefits for failing to participate in the Work Programme alone.

"That figure must now have doubled. Today's decision should mean that many of those subjected to benefit sanctions will be entitled to reimbursement by the Department for Work and Pensions.

"It is truly extraordinary that the government has found itself in this position by failing to provide basic information to those affected."