Jeremy Corbyn has condemned the IRA’s bombing campaign during the Troubles after coming under pressure to distance himself from the group’s activities.
The Labour leader said the IRA’s actions were “completely wrong” because they killed civilians.
Mr Corbyn said on Friday he had “never met” the IRA and had only held talks with its political wing Sinn Fein.
But the Conservatives claimed comments by Diane Abbot in an interview on Saturday showed this was untrue.
Ms Abbott, a long-time ally of Mr Corbyn, told LBC radio he had only met IRA members “in their capacity as activists in Sinn Fein”.
“I think we have to distinguish between conducting private meetings and supporting violent attacks and actually being on a platform,” said the shadow home secretary.
And she compared Mr Corbyn’s links with the Irish republican movement to the way former Prime Minister Tony Blair had negotiated with Sinn Fein during the peace process.
The shadow home secretary was questioned about remarks of her own made in a 1984 interview about Northern Ireland, where she said: “Every defeat of the British state is a victory for all of us.”
Ms Abbott said: “It was 34 years ago. A few years later I became an MP… I have moved on in the intervening 34 years.”
Conservative Foreign Secretary Boris Johnson has used her remarks to launch an attack on the Labour leadership: “Jeremy Corbyn’s lies have been exposed by his own shadow home secretary.
“Just hours after Corbyn claimed he had never met the IRA, Diane Abbott says he did – and she disgracefully sought to defend it.
“It is increasingly clear that Jeremy Corbyn will make up anything in an attempt to mislead voters.
“He’s pretending he didn’t support the IRA, just like he is pretending he won’t raise taxes and pretending he will replace our Trident nuclear deterrent.”
Mr Corbyn has faced questions over his meetings with Sinn Fein, the political wing of the IRA, during the 1980s and 1990s and his views on the republican movement during that period.
He repeatedly insisted in an interview with the BBC’s Andrew Neil on Friday that he had been working for a peaceful solution in Northern Ireland and that there “had to be a dialogue”.
On Saturday morning Mr Corbyn took part in a training session with youngsters on a visit to Hackney Marshes football pitches, in north London, where he launched plans to offer football fans a “flexible football ticket” to help more people attend matches.
Asked about his reaction when Downing Street and then-Prime Minister Sir John Major were targeted in an IRA mortar attack in 1991, Mr Corbyn said: “Obviously appalled.
“I was in Parliament at the time, I heard the attack go off… The bombing campaign was completely wrong because it was taking civilian lives and there had to be a process that dealt with the basis of it in Northern Ireland.”
That had come about through the subsequent peace process, he said, beginning on the nationalist side in talks between Sinn Fein’s Gerry Adams and the leader of Northern Ireland’s moderate nationalist SDLP party.
But former Work and Pensions Secretary Iain Duncan Smith, who was a captain in the British army during the Troubles, demanded an apology from the Labour leader, claiming he had tried to place British troops “like myself” on “an a equal par with terrorists blowing people up”.
“The troops were sent to Northern Ireland to uphold the peace. We were not sent to kill and maim indiscriminately. The IRA chose to bomb civilians indiscriminately… they did not care who they killed and maimed,” said Mr Duncan Smith.
“To equate what they did with British soldiers that were trying to uphold the peace is outrageous and that is what he [Mr Corbyn] has never apologised for or explained himself.”
He said that was why Mr Corbyn’s “judgement was so in question and that is why his disgraceful comments yesterday make him unfit to lead this great country of ours”.