Tory work and pensions secretary Iain Duncan Smith is facing calls to apologise after he misled voters about sensitive information on benefit-related deaths that was unearthed by Disability News Service (DNS).

Duncan Smith was one of five politicians taking part in a social security debate on the BBC’s The Daily Politics, alongside Labour, the Liberal Democrats, UKIP and the Greens, just two days before the general election.

The work and pensions secretary appeared to lose his cool after being criticised by the Greens’ Jonathan Bartley, who accused him of a “huge compassion deficit”.

After he had been told by presenter Andrew Neil that an Institute for Fiscal Studies report had concluded that the poorest had been hit hardest by his benefit reforms, Duncan Smith insisted that the aim of the reforms had been to move people off benefits and into work.

But Bartley, work and pensions spokesman for the Green party, pointed to secret reviews carried out by Duncan Smith’s department into benefit-related deaths, and asked him why he was refusing to publish them.

Freedom of information requests from DNS have revealed that the Department for Work and Pensions (DWP) has carried out 49 secret reviews into benefit-related deaths since February 2012.

DWP has also admitted to DNS that 40 of the 49 reviews were carried out following the suicide or apparent suicide of a benefit claimant.

The information watchdog is currently investigating DWP’s refusal to publish the 49 reviews, after a complaint was lodged by DNS.

But despite that investigation, and the DWP responses admitting that the reviews had taken place, Duncan Smith told Bartley there had been no reviews, and accused him of making “scurrilous” allegations.

He said: “I reject that, that’s just scurrilous, that’s really scurrilous.”

And Duncan Smith said he was “not prepared to accept cast-off allegations”, before warning him: “You make an allegation like that, you cannot stand that up, and I simply say to you, be very careful, no, be very careful, you say you are a Christian, be very careful what you say about people’s motivations.”

He added: “No, we have not carried out a review, and what I am telling you now is what we absolutely know is that you cannot make allegations about individual cases, in tragic cases, where obviously things go badly wrong, you cannot suddenly say this is directly the result of government policy.

“You make an allegation, which is what you do, and you hope that that will stick, and if it sticks then somehow you can point the finger at somebody.

“I can promise you I would never allow that to happen, I would never allow that to happen. What you said was cheap.”

Duncan Smith’s denial caused dismay and outrage on social media among many disabled campaigners, who knew DWP had admitted carrying out the reviews in freedom of information responses to DNS.

Michelle Maher, who tweets at @mmaher70, pointed out that Duncan Smith’s Tory ministerial colleague Esther McVey had even admitted to the work and pensions select committee (question 243) that the reviews had taken place.

Afterwards, Bartley told DNS: “Whether it is through a lack of knowledge or an attempt to deliberately mislead, Mr Duncan Smith’s denial is shocking.

“He should release the information that his department holds about the deaths immediately.”

The Green party later called on Duncan Smith to issue a formal apology for misleading the public about the DNS research.

Bartley said: “It is utterly shameful for Iain Duncan Smith to have misled the public and the families of those affected by these tragic deaths.

“It’s not enough that his department appears to have sat on research revealing the immense damage his welfare policies are causing to families up and down the country.

“To deny all knowledge of the reports is heartless and blinkered – hardly the kind of approach we want the person in charge of national welfare to be taking.”

Bartley said the party was now calling on DWP to publish the reviews on its website.

He added: “Understanding the impact of government policies is essential in helping us improve and inform future government decisions so that we can ensure they are working in the best interests of the public.

“That is exactly why it needs to be shared publicly and in an open and democratic manner.”

A Conservative party spokesman told DNS this afternoon (Wednesday) that Duncan Smith’s responses had been “completely accurate” because Bartley had been asking about a single review of benefit-related suicides and there had not been “a single review into any links between suicides and anyone’s welfare claims”.

He said: “It is standard procedure on a case-by-case basis if somebody who has interactions with DWP commits suicide then there is a standard peer review to make sure that the relationship was handled in a correct way and the DWP acted in a proper manner.

“This is not the same… as a review into causality. It is scurrilous to suggest there are links between these two things [government policy and suicides].”

But when DNS pointed out that Bartley had later asked Duncan Smith about the multiple reviews, and the work and pensions secretary continued to deny that they had taken place, the spokesman said: “I have explained why what he said was accurate. I completely understand that you have your point-of-view.

“My answer is that he is correct in saying that there has not been a review into the relationship between individual welfare claimants and cases of suicide.”

When DNS pointed out that DWP had admitted that it had carried out 40 reviews into benefit-related suicides, he said: “There has not been a review. They are on individual cases. They are standard procedure.”