Investigations into 60 cases where benefit claimants are said to have died by suicide have been carried out by the Department for Work and Pensions (DWP).
Labour's Diana Johnson said the figures cast doubt on claims that there is no link between suicide and welfare re-assessments, with DWP carrying out the internal reviews in the last five years.
The number of investigations has been falling each year, with ministers insisting the matter was taken extremely seriously.
But the figures have reignited the debate on how DWP treats vulnerable benefit claimants.
Ms Johnson told the Press Association: "Ministers have repeatedly claimed there to be no link between suicide and welfare re-assessment whenever figures have come to light.
"This parliamentary answer to me blows this claim out of the water.
"If there was no link, there wouldn't have been 60 reviews of suicides in the past five years.
"I am appalled that these figures have remained unpublished for so long."
A written parliamentary question from the Hull North MP has revealed that DWP carried out 15 internal reviews into suicides or alleged suicides of so-called DWP "clients" in 2012/13.
Fourteen reviews were carried out in each of the following two years, with 11 reviews in 2015/16.
This then fell to six last year.
"Families who've been left in the dark need to know everything the DWP knows about these cases," Ms Johnson said.
"Most importantly, we need a welfare system that supports, rather than victimises, the poorest and most vulnerable in our society."
In his answer to Ms Johnson, work and pensions minister Damian Hinds said the internal reviews were carried out in relation to suicides or alleged suicides.
He had previously told Labour MP Luciana Berger: "Suicide is a tragic and complex issue which we take extremely seriously.
"If information is received that a DWP client has attempted or completed suicide and it is alleged that DWP activity may have contributed to this, we carry out an internal review to establish whether anything should have been done differently."
Assessment for benefits has been an ongoing controversy for DWP, particularly the effects they can have on those with mental health issues.
Samantha Nicklin, head of campaigns at charity Rethink Mental Illness, said there was never a simple explanation for why people decide to take their own life.
She added: "What we do know is that people with mental illness consistently find the welfare benefits system - the interview, the sanctions, the number of assessments - stressful and harmful to their health.
"Currently the system is fundamentally unsuited to supporting people living with mental illness.
"We hope that the next government will use this opportunity to conduct an overhaul of the system, including the nature of the assessments, to ensure that people are not needlessly penalised and everyone can get the support they need."
Last year campaigners led by the Disability News Service successfully appealed to a tribunal that these internal reviews should be made public.
Recommendations from these reviews showed that DWP staff repeatedly failed to follow strict guidelines on how to support benefit claimants who had expressed thoughts of self-harm or threatened to take their own lives, which were introduced in 2009.
Anita Bellows, from Disabled People Against Cuts, which was among the groups that launched the appeal, said it was not surprising there were further cases that DWP had needed to review.
She added: "DWP now admits that the peer review process lacked 'robust governance' and has decided to improve its processes.
"It is too late for these claimants who took their own lives and it might be still inadequate if DWP is not prepared to look beyond procedure compliance."
Research by academics at Edinburgh's Heriot-Watt and Napier universities last month found that work capability assessments were causing permanent damage to some claimants' mental health, from which they were not recovering.
It also established, through dozens of in-depth interviews of people who had been through the tests, that "in the worst cases, the WCA experience led to thoughts of suicide".
A DWP spokesman said: "Any suicide is a tragedy and the reasons are complex, therefore it would be inaccurate and misleading to link it solely to someone's benefit claim.
"The department takes the safety and wellbeing of claimants very seriously, which is why we review our processes and procedures to ensure people get the right support that they need.
"We also spend around £90 billion a year on working age benefits to provide a vital safety net for some of the most vulnerable people in our society."