SINN Fein leader Gerry Adams has defended the involvement of Lord Louis Mountbatten's murderer in Sinn Fein's election campaign.
Thomas McMahon – the only person convicted for the horrific IRA attack in 1979 that also killed two children – has been canvassing for MEP hopeful Matt Carthy.
Despite being a convicted child killer, the party has described his contribution to the campaign as "valued".
McMahon served almost 20 years in prison for the callous bomb attack on Lord Mountbatten and his family while they were fishing off the Sligo coast.
The massive explosion claimed the life of Lord Mountbatten (79), his 14-year-old grandson Nicholas Knatchbull, and Paul Maxwell (15), who was working on the boat.
Another passenger on the boat, Lady Brabourne (82), died of her injuries the following day and Nicholas Knatchbull's twin brother Timothy was blinded in one eye.
Yesterday, Paul Maxwell's father John said he did not want to comment on McMahon but friends of the family said they found his involvement "distasteful".
McMahon has never apologised to Mr Maxwell or Lord Mountbatten's family for the terrorist attack.
Fianna Fail leader Micheal Martin said Mr Adams' support for the IRA killer was a "slap in the face" for the victims of the murders that shocked the nation more than 30 years ago.
Speaking to the Irish Independent, Mr Martin said: "Like a lot of people, I have watched with growing concern as Sinn Fein seeks to minimise and justify some of the most horrific and cruel episodes of their terror campaign.
"But even in this context, Mr Adams's defence of a colleague who killed a 14- and a 15-year-old child is particularly shocking."
Asked if he would like to distance himself from the convicted murderer, Mr Adams said he "values the contribution of every single republican".
"We are glad to have every single person who believes in a united Ireland, peacefully and democratically reached, to work with us," he said.
"Fianna Fail, Fine Gael and the fledgling Labour Party were made up of people like Tommy McMahon and others," he added.
Mr Adams insisted the British royal family's welcome for Martin McGuinness to Windsor Castle earlier this year showed reconciliation had been reached.
"If the family of Lord Mountbatten and others can be part of that hugely significant, symbolic building of the peace process then I think it's time for others in the media to move on also," he said.
Since his release from prison, under the terms of the Good Friday Agreement, McMahon has been an active party loyalist in the Monaghan area.
He is currently working on Sinn Fein candidate Matt Carthy's European election campaign.
He previously worked on Mr McGuinness's failed presidential election campaign in 2011.
McMahon's wife Rose is a former Sinn Fein Carrickmacross town councillor.
She was co-opted into the seat in 2008 when Sinn Fein councillor Eamon Conlon left politics but she failed to get re-elected the following year.
McMahon has reportedly been seen putting up posters and canvassing with Mr Carthy ahead of tomorrow's election.
Mr Carthy, who is likely to take a seat in Europe, denied McMahon would be co-opted into his council seat if he is elected to the European Parliament.
"I wouldn't imagine Tommy would be interested," Mr Carthy said. "He is a Sinn Fein member in Carrickmacross and he would be involved like any other party activist.
"Tommy McMahon spent almost 20 years in jail, he served the time. He is a Sinn Fein member now and he is actively involved in his local community."
McMahon was charged with the Mountbatten murders after gardai found traces of the chemicals used to make the deadly bomb on his clothes.
He served the majority of his sentence in Portlaoise Prison where he and others staged a failed escape attempt in 1985.
Three years later he fired a shot from a gun he smuggled into a holding cell in the Four Courts in Dublin.
He has since claimed he turned his back on the IRA.