Campaigners have called for an investigation into the deaths of at least 2,380 people within weeks of being judged "fit for work" by controversial assessments and moved off sickness benefit.
Learning disability charity Mencap said the figure - released by the Department for Work and Pensions following Freedom of Information Act requests - was "tragic" and raised questions about the fairness of the work capability assessment.
And TUC general secretary Frances O'Grady said the "disturbing findings cannot be swept under the carpet".
The DWP, which was ordered by the data watchdog to publish the statistics, insisted "no causal link" could be drawn between benefits status and the likelihood of dying as the individual causes of the deaths were not recorded.
Overall, death rates for unemployed claimants had remained in line with trends in the wider population for a decade, it stressed.
Critics called for a rethink of the system used to decide whether people can be moved from receiving Employment Support Allowance - the replacement for Incapacity Benefit - to standard unemployment benefit, meaning a £30 per week reduction in state help.
The figures showed that between December 2011 to February 2014, 2,380 died within around two weeks of ESA claims stopping following a decision that they were "fit to work".
A total of 1,340 died within the same timescale after appealing against a "fit to work" assessment - thought it is not recorded what proportion of those appeals were successful or failed.
Mencap said the numbers appeared unusually high for people of working age who had so recently been declared fit.
The charity's Rob Holland, who co-chairs the Disability Benefits Consortium, said: "These tragic figures are concerning and warrant further investigation.
"We know the fit for work test is failing disabled people, with devastating consequences. Wrong decisions can mean people are left with little or no support at all, in some cases struggling to pay for their homes and basic essentials like food and heating.
"The Government must act now to reform the work capability assessment so it is fair for disabled people and those with health and medical conditions. Indeed there is real concern that the process itself is stressful and can in fact worsen people's conditions."
Ms O'Grady said: "We urgently need an inquiry into the Government's back-to-work regime.
"The fact that more than 80 people are dying each month shortly after being declared 'fit for work' should concern us all. We need a welfare system that supports people to find decent jobs not one that causes stress and ill health."
Mike Sivier, one of several campaigners who submitted FOI requests, welcomed the publication, saying the DWP had "caved in completely" by releasing the actual numbers of deaths.
He suggested he might now push for details of the causes of death in each case - including cases of suicide.
A DWP spokesman said: "We don't hold information on reason of death, so no causal effect between a fit for work decision and death should be assumed.
"The mortality rate of those who are claiming Jobseeker's Allowance - which includes some of those found fit for work - is still lower than for the general population.
"Furthermore, the overall trend shows the mortality rate for people who have died while claiming an out-of-work benefit, has fallen over a 10-year period."
Shadow work and pensions minister Kate Green said: "These figures should be a wake-up call for the Government.
"Ministers need to focus on sorting out the assessment process so that everyone can have confidence in it, and providing support for disabled people who can work in order to help them do so."
Labour leadership candidate Andy Burnham said they were "shocking figures that for the first time show the human cost of this Government's punishing benefits regime".
"We now need an urgent national debate about these figures, and if elected Leader I would call a full-day debate in Parliament at the first available opportunity."