The head of an influential cross-party committee of MPs has criticised the “incredible secrecy” surrounding the government’s handling of the deaths of vulnerable benefit claimants following the case of Errol Graham, a severely ill man who died of starvation after his benefits were cut off.

Stephen Timms MP, the chair of the Commons work and pensions committee, is to ask ministers why, despite scores of internal Department for Work and Pensions inquiries into claimant deaths – many of them as a result of suicide – in recent years, officials were unable to show what they had done to improve the safeguarding of vulnerable claimants.

“The idea that people are taking their own life as a result of DWP actions is so awful,” Timms said. “It is unacceptable for the DWP to keep obfuscating. It cannot avoid the subject any longer. This is clearly something serious and it needs to engage and resolve it.”

The emaciated body of Graham, 57, who had severe depression, was found by bailiffs seeking to evict him from his flat in June 2018, just months after his benefits were stopped after he failed to attend a meeting with welfare officials.

Profile Errol Graham's letter for welfare officials Show At the inquest into Errol Graham's death, the coroner, Elizabeth Didcock, said this handwritten letter was one of the few sources of information describing his state of mind in his last years. It was undated and never sent, but reads as if intended to be taken along to the work capability assessment that would decide whether he would remain eligible for disability unemployment benefit. Dear Sir/Madam, I’ve had to put in writing how I feel as I find it hard to express myself. I wish I could feel and function normally like anyone else but I find this very hard. I can’t say I have a typical day because some are good, not many, clouded by very bad days. I get up as late as I can so that the day doesn’t seem too long. On a good day I open my curtains, but mostly they stay shut. I find it hard to leave the house on bad days. I don’t want to see anyone or talk to anyone. It’s not nice living this way. I’m afraid to put my heating on and sit with a quilt around me to keep me warm. I dread any mail coming, frightened of what it might be because I don’t have the means to pay and this is very distressing. Most days I go to bed hungry and I feel I’m not even surviving how I should be. Little things that people brush off are big things to me. I have come on my own today because I have been unable to share how I feel with anyone because I don’t think they would understand. It has made me ill to come here today. It is a big ordeal for me. My nerves are terrible and coping with this lifestyle wears me out. Sometimes I can’t stand to even hear the washing machine and I wish I knew why. Being locked away in my flat I feel I don’t have to face anyone. At the same time, it drives me insane. I think I feel more secure on my own with my own company, but wish it wasn’t like that. I’m not a drinker and have never been so don’t think that I’m here to abuse the system. Please judge me fairly. I am a good person but overshadowed by depression. All I want in life is to live normally. That would be the answer to my prayers. Thank you to all for taking the time to read this letter, I really appreciate it. I don’t know how I’ll cope when I see you all. I hope I will be OK.

Timms cited a recent National Audit Office (NAO) report which revealed that the DWP had internally reviewed at least 69 suicides which could have been linked to problems with benefit claims over the last six years, ostensibly to improve its processes. The NAO found no evidence that the DWP had acted on any of the recommendations of those reviews, and the figures in the report did not include cases, like that of Graham, where suicide was not the formal cause of death.

The watchdog had investigated the DWP after Timms’s predecessor as work and pensions committee chair, the former MP Frank Field, had written to it to complain that officials had blocked his requests for data on benefit claimants who had killed themselves on the grounds that gathering the information would be too expensive.

Concerns over the DWP’s treatment of vulnerable claimants have risen after recent revelations about the death of Graham, who had claimed disability unemployment benefits for years because of severe mental illness, which manifested itself in depression, self-harm, attempted suicide and acute social anxiety.

At an inquest into his death last year, it was revealed that although the DWP’s attempts to contact Graham to inform him his benefits were at risk were unsuccessful, officials cut them off anyway. They did not inform his GP, landlord, family or the police about what they had done.

Asked by the coroner whether this was reasonable given Graham’s medical history, a DWP official said that under current official safeguarding guidance they had technically fulfilled their duties and this course of action was the “right thing to do”.

Last week, lawyers acting for Graham’s family launched a legal action against the DWP, claiming it unlawfully failed to take reasonable steps to check on the health of a claimant they knew to be highly vulnerable before removing his only source of income.

There is also confusion over commitments made under oath by a senior DWP official at Graham’s inquest last June. A transcript seen by the Guardian shows that the DWP’s chief psychologist, David Carew, told the coroner a safeguarding review would report in the autumn, but the DWP now says that no final report exists.

Responding to repeated questions by the coroner, Elizabeth Didcock, Carew insisted that the wide-ranging review was taken seriously by the DWP and was urgently looking at a range of measures to protect highly vulnerable claimants at risk of having their benefits cut off, including changing safeguarding guidance to staff.

As a result of Carew’s intervention, the coroner decided against writing a prevention of future deaths report, which would have required the DWP to formally explain what steps it was taking to improve its safeguarding policy.

“We have work to do and I leave this building today very clear in my own mind that the work we are involved in at the current time has a degree of urgency about it,” Carew told the coroner.

However, the DWP, asked to explain what had happened to the report cited by Carew by the Disability News Service website this week, said there was no review team, that safeguarding prevention work was “ongoing”, there was “no final report” and no formal commission to publish a review.

The disability minister, Justin Tomlinson, told MPs last week the DWP had set up an internal serious case panel which would meet quarterly to consider benefit-related deaths and learn from issues that arose related to them. A DWP spokesman said: “Our sympathies are with Mr Graham’s family. It would be inappropriate to comment further at this time.”

The Labour MP Debbie Abrahams, who last week read out in parliament the names of 24 people whose deaths followed problems with the benefit system, called for an independent inquiry, adding: “This may go some way to restoring confidence in the DWP.”

In the UK and Ireland, Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at www.befrienders.org.