Leo Varadkar has said the Republic of Ireland cannot have a taoiseach (prime minister) that does not view Troubles atrocities as crimes.
The tánaiste (Irish deputy prime minister) and Fine Gael leader made his remark in response to a comment by Sinn Féin leader Mary Lou McDonald.
Last weekend she had said there was “no comparison” between the IRA and gangland violence.
Mr Varadkar also ruled out going into a coalition government with Sinn Féin.
Speaking on the Indo Daily podcast, he said that any taoiseach should be clear that killings during the Troubles were crimes.
“I don’t think we can have a taoiseach in this country who is unable to say that the killing of innocent children, guards, prison officers, members of Defence Forces, is not a crime,” he added.
“If she wants to say it was a war and they were war crimes, fair enough, but she has to be able to say that.”
Widow of IRA victim criticises McDonald’s comments
Mr Varadkar said that he would prefer to go into opposition than try to govern with Sinn Féin.
He said he viewed the party as “high-tax, anti-trade” and “Eurosceptics”.
“We will not consider coalition with Sinn Féin… oil and water doesn’t mix,” he said.
It’s not just about the past, although those issues are important – it’s more about the future.
“If that was the choice before me and Sinn Féin was in a position to lead a government, we’re going to need a strong, democratic opposition party that’s able to hold them to account, restrain them, curb their excesses, replace them and clean up the mess.
“I think cleaning up the mess could take 10 years.”
‘Murder is murder’
Ms McDonald had made her comment in an interview with the radio station Newstalk.
She was asked about gangland violence and said there was “no comparison” between such criminality and IRA violence during the Troubles.
“As somebody who represents the north inner city of Dublin and who has seen at first hand the corrosive damage that gangland [crime] has caused to communities, there is absolutely no comparison,” she said.
“Things that happened in the course of a very long political conflict – which thank God is now long over, we have had 25 years of peace – there is no comparison between that and the kind of challenge… that this vicious so-called gangland crime epidemic poses.”
Her comment was criticised by the widow of An Garda Síochána Detective Jerry McCabe, who was shot dead by the IRA in 1996.
Mr McCabe was killed and his colleague was injured during an armed raid on a post office van in Adare, County Limerick.
Four Provisional IRA members were convicted of the manslaughter of Mr McCabe.
“No matter who commits murder, murder is murder”, his widow Ann told BBC Radio Ulster’s The Nolan Show.
She said she believed there was no difference between the IRA men who killed her husband and any other criminals.