Northern Ireland's deputy first minister Martin McGuinness has said his "heart goes out" to protesters at a lecture he has given in a town which suffered an IRA bomb attack in 1993.
Two boys died when two bombs exploded in Warrington 20 years ago.
Mr McGuinness, who was previously an IRA leader, was giving the town's annual peace lecture.
But one opponent, Julie Hambleton, said it was like "asking Myra Hindley to give a talk on child protection".
Mrs Hambleton, whose sister Maxine died at the age of 18 in the Birmingham pub bombings carried out by Irish Republicans in 1974, was one of a small group of people protesting outside the Tim Parry-Johnathan Ball Foundation for Peace building.
The centre takes its name from the two boys who lost their lives in the attack, aged 12 and three.
Tim Parry's father Colin asked Mr McGuinness to give the lecture, which is held every year in the centre, when they met in Belfast earlier this year.
Speaking before he gave the lecture, Mr McGuinness said he "understood" the objections and empathised with those who could not make the "journey" he had to peace.
"My heart goes out to them because they too are people that have suffered as a result of the conflict in the north of Ireland," he said.
He previously visited the centre in 2001, when he said the bombing was wrong.
He added on this visit that it was "absolutely shameful" that the boys had lost their lives.
"We need to be sorry for everything that happened - all of us who were involved in the conflict, not just Irish Republicans," he said.
The brother of Maxine Hambleton, Brian, who was also protesting, said Mr McGuinness had a "murky, violent past" and it was "immoral" for Mr Parry to have asked him to deliver the lecture.
Mr Parry said he accepted such criticism but that it did not "grasp the founding principles of this organisation, which is to be peace builders with the aim of reconciling people".
"Once you set your stall out in that regard, you don't close the door to certain people and open it to others," he said.
No-one has been charged over the attack, in which two bombs hidden in litter bins exploded in Bridge Street, killing the two boys and injuring 54 others.
Mr Parry and his wife Wendy opened the centre on the seventh anniversary of the bombing.
In 2007, Sinn Fein leader Gerry Adams apologised to them at a meeting in London.
Johnathan Ball's parents have since died.