The victims of the 1974 Birmingham pub bombings were "accidental deaths" in an "IRA operation that went badly wrong", its former intelligence chief told an inquest.
Kieran Conway from Dublin said the attacks were "not sanctioned" by the IRA and public outrage at the attacks "nearly destroyed" the group.
Following what he called the "disaster in Birmingham" on the night of November 21 by a provisional IRA active service unit, "the dip in public support was extraordinary".
Mr Conway, who robbed banks for the IRA in the 1970s, added: "The IRA was only saved by the subsequent (ceasefire) talks with the British Government."
The blasts at the Mulberry Bush in the base of the city's iconic Rotunda and the basement Tavern in the Town in nearby New Street killed 21 people and injured 220 more.
Bereaved families have waited 44 years for fresh inquests, which are now in their fourth week.
Asked who bore responsibility for the attacks, Mr Conway said: "I accept everybody collectively involved in the IRA at that time bears a full and awesome responsibility for what happened at Birmingham and for the deaths of all those people."
Mr Conway, speaking over a video link from a secure location, was also asked if he knew the identities of the bombers.
He said he knew only from "third-hand" reports in newspapers, books and TV documentaries that were in the public domain.
In any case he added he would not name any "IRA men" who were still alive.
Barrister Kevin Morgan, asking questions on behalf of the bereaved victims' families, asked: "Would you agree that the killings in Birmingham on November 21 1974 constituted murder?"
Mr Conway, who was convicted of handling explosives in Londonderry, Northern Ireland, in the 1970s, replied: "No I don't agree. I believe it was an IRA operation that went wrong.
"Had the IRA deliberately targeted that pub with the intention of killing civilians then that would have been murder, yes.
"But in the circumstances, as I have been told, I don't accept that it was murder.
Asked how he would have described the deaths, he added: "I understand perfectly that this is unacceptable to the British people but I would categorise them as accidental."
During a statement about the bombings he gave to An Garda Siochana on behalf of West Midlands Police in January 2016, Mr Conway referred to the killings as "being murders", jurors were told.
Mr Conway, who is a criminal defence solicitor in Ireland, told the inquest he used "the wrong word" in that interview.
After the attacks, an internal IRA court of inquiry, convened in Ireland, cleared those involved in the bombings, Mr Conway added.
He said IRA chiefs agreed with the "initial explanation" the "atrocity" was down to the delay in calling in the coded warning because the chosen phone box was out of order.
"No court martial ever took place," he added, and no IRA members were ever internally disciplined over the attacks.
Coroner Peter Thornton QC asked Mr Conway if the the faulty phone box story could have been a "well-orchestrated and convenient lie" for the bungling bomb team to tell their superiors and escape punishment.
Mr Conway agreed it could have been but denied the leadership would have "looked for an excuse" as well.
He said the IRA Army Council chairman David O'Connell was "lying" when, just weeks after the bombings, he claimed the IRA was still investigating if its men were to blame.
"Essentially he was lying, he knew perfectly well what had happened," said Mr Conway, who earlier described O'Connell as an "honourable man".
Mr Conway said, at the time of the bombings, IRA operations in England were carried out by active service units "autonomous" of the organisation's command in Ireland, and were picking bombing targets themselves.
He said nobody in the IRA's Army Council, which ran military operations, or the organisation's commanders in England had any idea the pubs were to be targeted.
Speaking of his own feelings on the bombings, he added: "The bombings had been careless if not downright incompetent."
Mr Conway told jurors O'Connell had personally told him the attack "was not sanctioned by them".
He added the stated policy of the IRA - which he described as being "at war" with the British state at the time - was civilian targets were "strictly and loudly forbidden".
He added: "Those targets ought never to have happened. I have said that many times.
"It was a civilian pub, there was no question of it being a pub with which soldiers commonly drank - and it was not. It was not a permissible target."
The inquests continue.