Coalition claims that it has presided over a jobs revival have come under fresh scrutiny with research showing that as few as a fifth of the 2 million jobless people whose benefit has been taken away are known to have found work.

The research, due to be presented at a Commons select committee inquiry into welfare sanctions on Wednesday, suggests that hundreds of thousands are leaving jobseeker’s allowance because of benefit sanctions without finding employment, though the report’s authors decline to provide an exact figure.

Written by academics at the University of Oxford and the London School of Hygiene & Tropical Medicine, the report raises questions about why so many of those losing their benefit then disappear from the welfare system – possibly to rely on food banks.

Prof David Stuckler, of Oxford University, said that benefit sanctions “do not appear to help people return to work. There is a real concern that sanctioned persons are disappearing from view. What we need next is a full cost-benefit analysis that looks not just narrowly at employment but possibly at hidden social costs of sanctions.

“If, as we’re finding, people are out of work but without support – disappeared from view – there’s a real danger that other services will absorb the costs, like the NHS, possibly jails and food support systems, to name a few. Sanctions could be costing taxpayers more.”

However, the Department for Work and Pensions, which is expected to hail a further rise in UK employmenton Wednesday, countered that it was proud that 1 million jobless people were now subject to the “claimant commitment”, which sets out tougher requirements on the jobless to find work or risk losing their benefit payments.

Iain Duncan Smith, the work and pensions secretary, said: “It is only right that in return for government support – and in return for their benefits – jobseekers are expected to do all they can to find work. Although on benefits, they still have a job: the job is to get back into work.

“The claimant commitment, which is deliberately set to mimic a contract of employment, makes this expectation explicit. It has created a real change in attitudes. Already more than a million people have signed up to – and are benefiting from – this new jobseeking regime.”

The Oxford-based research showed that between June 2011 and March 2014, more than 1.9m sanctions were imposed on people receiving jobseeker’s allowance (JSA), with 43% of those sanctioned subsequently ceasing to try to claim the benefit. Only 20% of those who left gave as their stated reason that they had found work.

The Department for Work and Pensions conducts no systematic research into what happens to those sanctioned, so the new findings start to fill an evidential gap in what has been one of the biggest but least publicised changes to the welfare system since the government came to power.

The 1.9m benefit removals between June 2011 and March 2014 represent a 40% increase compared with the previous seven years. The figures are based on official monthly and quarterly data from databases covering UK local authorities between 2005 and 2014.

The highly emotive dispute about a central aspect of government welfare reform centres on whether jobcentre staff, driven by senior management, are following arbitrary and poorly communicated rules that punish not just the feckless but some of the most vulnerable in society, including mentally ill and disabled people. Many independent witnesses have urged the DWP inquiry at least to suspend the sanctions regime for those claiming employment support allowance, the main disability benefit .

Study author Dr Rachel Loopstra, from Oxford University, said: “The data did not give us the full picture of why sanctioned people have stopped claiming unemployment benefit. We can say, however, that there was a large rise in the number of people leaving JSA for reasons that were not linked to employment in association with sanctioning. On this basis, it appears that the punitive use of sanctions is driving people away from social support.”

The study also shows widespread variation in how local authorities used sanctions. In Derby, Preston, Chorley and Southampton, researchers found particularly high rates of people being referred for sanctions. In some months, more than 10% of claimants in these areas were sanctioned – the highest rates nationwide.

Co-author Prof Martin McKee, from the London School of Hygiene & Tropical Medicine, said: “There is a need for a cost-benefit analysis of sanctioning, looking at it not just in narrow terms of unemployment benefit, but also the bigger picture, focusing on employment, health, and other social costs.”

He added: “The coalition government has embarked upon an unprecedented experiment to reform social security. I hope policymakers will be informed by these findings and see the value of investigating the consequences.”

Separate evidence in front of the DWP select committee inquiry includes witness statements from former jobcentre staff suggesting senior management threaten staff if they do not take a harsh approach to claimants. There is also cumulative evidence that many of those sanctioned have little or no knowledge of why they are being punished.

The main union representing jobcentre staff, PCS – also due to give evidence on Wednesday to the select committee inquiry – suggests: “While there is considerable anecdotal evidence about the inappropriate use of sanctions, there is a lack of empirical evidence. We believe that DWP should publish a more detailed breakdown of sanctions, and specifically more detailed explanations as to why they were imposed. PCS’s survey of our adviser members showed that 61% had experienced pressure to refer claimants to sanctions where they believed it may be inappropriate to do so.”

DWP select committee inquiry member Debbie Abrahams said: “This government has developed a culture in which Jobcentre Plus advisers are expected to sanction claimants using unjust, and potentially fraudulent, reasons in order get people “off-flow”. This creates the illusion the government is bringing down unemployment.”

The government counters that its policies are turning the UK into the jobs factory of Europe, and dismisses the idea that the unemployment figures are being subverted by sanctions.

A DWP spokesman said: “As the authors admit themselves the data does not give a full picture. What we do know – according to independent figures from the Office for National Statistics – is that we now have a record number of people in employment in this country and there are two million more people in private sector jobs compared to 2010.”