Jobseekers have been made to do compulsory unpaid work for up to four weeks after refusing to take part in the voluntary work experience scheme.

The revelation, supported by documents released through the Freedom of Information Act, calls into question the concessions made to the voluntary programme last month, which removed a two-week benefit sanction imposed on those dropping out of that scheme, as refusal to complete a placement on the compulsory scheme can lead to jobseekers' benefits being stopped for three to six months.

Others have reported being placed on mandatory work schemes just weeks after signing on to claim unemployment benefits.

Major employers, such as Tesco, and the business lobby group CBI met ministers last month amid mounting pressure on the voluntary work experience programme, which allows for unemployed people aged 16-24 to work unpaid for up to four weeks while continuing to receive benefits.

Businesses had come under fire from campaigners as it was revealed those dropping out of the scheme after a week faced their benefits being stopped. This pressure led to the withdrawal of the sanction.

However, several jobseekers who identified themselves to the Guardian and provided some details of their situations, allege they have been sanctioned through other means for refusing to participate in the voluntary scheme. As all are still either claiming jobseekers' allowance or are on still on their compulsory work placements, they have asked not to be identified.

One said he had initially accepted a voluntary placement under the belief he would be paid for the duration. When he learned he would not, he contacted his adviser.

"I asked her if it was too late to pull out, to which she responded with 'no'," he said. "I then told her that I indeed wanted to pull out of the scheme, and that I believed that I should have been informed more about the scheme as they had not told me that the store in question wouldn't be paying me."

A few weeks later, around seven months after first claiming his benefit, the jobseeker was placed on the mandatory work activity (MWA) scheme for four weeks – an unpaid placement of up to usually for a charity or public sector organisation. Jobseekers unemployed for less than a year are eligible for the scheme, and refusing to take part or dropping out of the programme leads to benefits being withdrawn for between three and six months.

The jobseeker believes his placement on the mandatory programme was linked to his attitude towards his adviser.

"I also told her that I believed that these private store chains should be hiring people, and not getting them to work at no cost to them," he said. "In hindsight, this is probably what led to me being put on the mandatory work activity scheme."

Another recounted dropping out of the voluntary work experience scheme – "the type of jobs were terrible" – and being given a two-week benefit penalty, only to be faced with a mandatory placement at a meeting soon afterwards, with a six-month benefit stoppage for refusal.

Another jobseeker provided details showing he had been placed on a compulsory work scheme just one week after refusing a voluntary work experience placement. Several other jobseekers, refusing to give specific details, reported similar experiences through Twitter and the Guardian's online submissions system.

The MWA programme was designed by the government to allow some jobseekers to "move closer to the labour market" and learn or re-learn disciplines such as timeliness, working under supervision and other work-related disciplines.

The government projected only around 10,000 jobseekers each year would be placed on the scheme, but by November 2011 – the latest set of statistics – MWA had overtaken the voluntary scheme, with 8,100 compulsory placements in the most recent month compared with 6,600 voluntary placements.

Guidance given to Jobcentre staff on mandatory work and obtained through freedom of information requests says advisers may, at their discretion, use dropping out or refusing to participate in voluntary schemes as grounds for MWA.

"A claimant 'dropping-out' of an employment measure prematurely may, or may not, indicate a lack of focus and discipline on their part," it states. "It is for advisory teams to consider the merits of MWA referral on a case-by-case basis."

The chancellor, George Osborne, had signalled in his autumn statement that young people who rejected the package of assistance on offer from the government could face mandatory work.

"Our new youth contract addresses both problems with the offer of private sector work experience for every young person unemployed for three months. After five months, there will be weekly signing on. After nine months, we will help pay for a job or an apprenticeship in a private business," he told the Commons.

"Some 200,000 people will be helped in this way but, as the deputy prime minister has said, this is a contract. Young people who do not engage with this offer will be considered for mandatory work activity, and those who drop out without good reason will lose their benefits."

Guidance states MWA should typically be used for jobseekers who have claimed benefits for longer than three months, but one individual said he was put on a placement just a fortnight after re-signing on to jobseekers' allowance (JSA) after finding a temporary job, and having claimed for less than six months in total.

"I am shocked that this is legal and am actually quite upset by the situation," he said. "But until I find work I have no choice but to participate in the scheme, as I couldn't live without JSA for 13 weeks."

A spokeswoman for the Department for Work and Pensions strongly rejected that mandatory placements would be used as a sanction, but said they could be offered in circumstances where advisers felt they were appropriate. In a statement, it was stressed that such referrals were not automatic.

"It is not the case that claimants who do not volunteer for work experience would automatically be referred to mandatory work activity," it said. "Jobcentre Plus advisers have the flexibility to use mandatory work activity, where they feel it is appropriate, as part of a wider range of support options. The decision to refer a claimant to mandatory work activity is taken on a case-by-case basis and claimants are only referred to the scheme where it is appropriate in their individual circumstances."

Speaking with regard to individuals being placed on mandatory programmes after just a few weeks of unemployment, the spokeswoman said: "We have said that we expect most referrals to mandatory work activity will be for claimants who have been unemployed for 13 weeks or more. However, we have not ruled out the possibility that some claimants may be referred before this point where Jobcentre Plus advisers consider this to be appropriate in their individual case."

With regard to the chancellor's comments, the DWP said: "We are currently considering the details of how mandatory work activity can best support the youth contract in helping young people to move into work."

• This article was amended on Tuesday 20 March 2012. The DWP made clear that mandatory work placement schemes last four weeks rather than eight. This has been corrected.