Former IRA commander Martin McGuinness said "his heart goes out" to protestors at a peace lecture he gave in a town bombed by the terror group.
Mr McGuinness, now the Northern Ireland Deputy First Minister, spoke in Warrington having been invited by Colin Parry, who lost his 12-year-old son in the bombing of the town in 1993.
Mr Parry, who has since set up a peace foundation in the name of his son, said while he has not forgiven the IRA for the bombing, history was "littered" with terrorists who had now become peace-makers.
A small band of around 12 demonstrators stood outside the venue last night protesting at Mr McGuinness' speech at the Tim Parry - Johnathan Ball Foundation for Peace.
Julie Hambleton, whose sister Maxine, 18, was killed in the Birmingham pub bombings, compared Mr McGuinness' giving a talk on peace to "asking Myra Hindley to give a talk on child protection".
Before the speech, Mr McGuinness said that he "understood" the objections and described the path to peace as a "journey".
"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.
"I fully appreciate that there are other people who don't feel able to make that journey. I would be the last to criticise them.
"My heart goes out to all the victims of the conflict.
"I feel very compassionate to all of them.
"We need to be sorry for everything that happened with the people involved in the conflict."
During his speech, he told of his own and Ulster's journey to peace and his hopes for the future, adding: "I was once in the IRA. I am now a peace builder.
"It has been a journey which has involved much hurt and pain.
"I have followed many coffins and stood beside many grieving families in the years since.
"But there can be no greater tragedy in life than parents having to bury their child. "
He added: "Regrettably the past cannot be changed or undone. Neither can the suffering, the hurt or the violence of the conflict be disowned by Republicans or any other party to the conflict."
Mr Parry said the foundation had an "open door" policy and their founding principle was that all opinions from opposing sides of conflicts were welcome in the pursuit of peace.
"I would hope that the people outside, rather than criticise us for that, would recognise that's a different path but an honourable path," he said.
Tim and Johnathan were killed when bombs planted in litter bins in the town's main shopping area were detonated shortly after midday on a sunny Saturday afternoon.
No warning was given and no one has been prosecuted for the outrage on March 20 1993, that left 56 people injured.
Johnathan, three, was in the town with his babysitter to buy a card for Mother's Day, the next day, when he was killed.
Tim, an Everton fan, had been shopping for football shorts when he caught the full force of the explosion. He died in his father's arms five days later in Liverpool's Walton Hospital.
The death of the two boys sparked a public outcry in the UK and on both sides of the border in Ireland.
Mr Parry and Tim's mother, Wendy Parry, have set up the Tim Parry Johnathan Ball Foundation for Peace, which has since become an internationally recognised centre for conflict resolution and victim support.
One of the protesters outside the venue was Brian Hambleton, 58, who dropped off his sister Maxine at the Birmingham pub blasted by IRA bombs on the evening of November 21, 1974.
Mr Hambleton, from Birmingham, said: "It makes me feel ill being within 100 yards of him.
"I'm here for a reason and that reason is that man's murky, violent past.
"He has to be answerable for his past before he goes forward with peace.
"He shouldn't be speaking in there, he should be on his knees begging people's forgiveness.
"This town lost two beautiful young boys like I lost my sister. How Mr Parry can greet him and invite him here is beyond me. It is immoral."