Speaking at a campaign rally in East Yorkshire, Mr Corbyn came under pressure from journalists to clarify his views on the militant group following accusations that he had “IRA sympathies”.
However, when asked whether he believed the organisation was guilty of terrorist activities, the Labour leader said only that he condemned “all acts of violence” that occurred during the Troubles.
This response was labelled “disgraceful” by Mr Corbyn’s critics, with Security Minister Ben Wallace suggesting it proved him “unfit” to be Prime Minister.
Mr Corbyn’s leadership has long been overshadowed by questions about his position on the IRA, after it emerged in 2015 that he attended commemorations to honour dead IRA members.
The issue came to a head over the weekend, after he repeatedly refused to denounce the group during an interview with Sky.
He was quizzed again during a Labour campaign event in Hull, that was intended to promote the party’s plans to create a £1 billion “cultural capital fund” to boost the country’s digital and artistic industries.
Asked whether he considered the IRA to be terrorists and if he would “unequivocally” condemn the organisation, he said he “condemned all acts of violence... from wherever they came” but stopped short of naming the IRA.
The Tories were quick to attack the Labour politician, with Mr Wallace arguing it was a “disgrace” that someone campaigning to become Prime Minister “cannot describe the IRA as terrorists”.
“To suggest otherwise is an insult to the victims and relatives whose lives were devastated by the IRA’s murderous campaign of violence,” he said. “Anyone who has ever experienced the fear and horrendous aftermath of indiscriminate bombings and shootings will know that the IRA were ruthless terrorists.
“No ifs, no buts, the IRA were terrorists who murdered hundreds of people and ruined thousands more lives. If Jeremy Corbyn cannot say that then he is unfit to be Prime Minister.”
The Democratic Unionist leader Arlene Foster also described Mr Corbyn’s behaviour as “abhorrent”. Speaking in London, she said: “Here we have a man who is putting himself forward to lead our nation and yet he cannot condemn an organisation which was taking away the fundamental human rights of British citizens.”
The visit to Yorkshire coincided with an address by shadow defence secretary Nia Griffith.
In a clear effort to distance herself from Mr Corbyn, Ms Griffith told an audience at the Royal United Service Institute: “I’m not going to speak for my leader, but ... as somebody who is old enough to remember the Troubles in Northern Ireland – I had friends who actually served in Northern Ireland – I absolutely and unequivocally condemn IRA bombings in Northern Ireland.”