Private firms awarded multimillion-pound contracts to run the Work Programme have advised that there should be many more cases where claimants have their benefits stripped as punishment for failing to seek work.

As part of its crackdown on welfare dependency, David Cameron's government has more than tripled the number of punishments enforced against failing jobseekers across all its schemes. The number of cases has risen from 139,000 benefit cuts under Labour in 2009 to more than 500,000 in 2011. Yet documents obtained by the research group Corporate Watch reveal how private firms on payment-by-result contracts have suggested that a much greater number of punishments should have been meted out to people on the Work Programme, a key part of the coalition's drive to "get Britain working".

In the first eight months of the government's flagship employment scheme, jobcentres agreed to cut benefits in about 40,000 cases. But figures contained in an internal Department for Work and Pensions analysis reveal private firms running the programmes actually referred almost three times as many (110,000) for sanctions. And critics say jobcentres are gradually upping the number of those denied benefits.

Richard Whittell from Corporate Watch said the Work Programme appeared to be focused on slashing benefit rather than putting people into work. "These figures give the lie to the government's claims its welfare reforms are about helping people into work," he said.

"By the time it's finished, more people will have been sanctioned by the Work Programme than properly employed through it. Every month thousands of people are having their only source of income stopped and being pushed into hardship. Companies like Serco, Working Links and G4S may not be very good at finding people suitable work, but they're dab hands at punishing them." The private firms say they make their referrals to job centres in line with government guidelines.

After a week in which the prime minister signalled his intention to hit those on benefits harder to create a more "responsible" society, the new figures suggest a hardening of attitudes towards the jobless, in spite of widespread misgivings about the fairness of the reforms already in place. Two claimants last week took the DWP to court over being forced to work for free.

Jobseekers can lose their benefits for up to 26 weeks for "refusal, without good cause" to attend an employment programme or carry out what is called a jobseeker's direction, a formal instruction to take certain action. They can also be punished for "refusing employment without good cause, or losing employment through misconduct".

The public-private partnership giant, Working Links, which boasts a turn-over of £123m and whose shareholders include Capgemini, referred the most cases for sanctions (11,910) between June 2011 and January this year. The jobcentres accepted the argument for cuts in 6,210 of those cases. A4e, which paid its former chairman Emma Harrison an £8.6m dividend in 2010, referred the second largest number of cases for punishment. The firm, which has been at the centre of a series of fraud allegations, requested sanctions in 10,120 cases. Jobcentres agreed to withhold benefits in 3,000 of those cases.

Other large contract holders leading the way in demanding punishment for benefit claimants included Serco, which has an annual turnover of £4bn a year. The outsourcing giant recommended punishment in 9,090 benefit claimant cases, but only 2,230 were approved.

Employment minister Chris Grayling said there was no financial imperative for private firms to punish jobseekers. "This government expects jobseekers to comply with the conditions of their benefit if they are receiving taxpayers' money," he added. The DWP said that the figures had not been confirmed by the Office for National Statistics.