Fianna Fáil leader Micheál Martin has insisted his party will not enter government with Sinn Féin, describing the party as IRA apologists and cult-like.
Speaking on Newstalk radio on Sunday, Mr Martin said any democratic party would have difficulties with Sinn Féin and its politics.
Mr Martin cited recent comments made by Sinn Féin president Gerry Adams in relation to the murder of Tom Oliver as a troubling picture of what the party stands for.
Mr Adams had said he did not believe Mr Oliver's killers should be prosecuted. Mr Oliver was murdered in 1991 by members of the IRA.
Speaking on Sunday, the Fianna Fáil leader said he fundamentally disagreed with the way Sinn Féin “takes an apologist approach to heinous crimes”.
Mr Martin also claimed the party attempts to re-write the narrative in relation to Northern Ireland and takes a very dangerous approach to politics.
He said: “It was only two years ago when the PSNI (Police Service of Northern Ireland) intelligence community made it clear the IRA still control Sinn Féin and their people.
“It is a very controlling organisation. They are still very strong apologists for the IRA.”
Mr Martin confirmed there was differing views in the party on a potential arrangement with Sinn Féin.
However he insisted the majority was clear that coalition with the party was a non-runner.
The Irish Times reported recently how a number of Fianna Fáil TDs believe the party should be open to coalition with Sinn Féin.
Sinn Féin has indicated it wanted to enter government as a junior coalition party but ruled out supporting a minority government.
Fianna Fáil will gather in Co Longford on Monday for a pre-Dáil meeting to discuss the upcoming term and Budget 2018.
When asked about the issue of the eighth amendment of the Constitution, Mr Martin said he believed it was time for a referendum on the matter.
He hoped it could take place next year but stressed there needed to be a very clear question put to the people.
As party leader, Mr Martin insisted he would not impose his personal views on members of Fianna Fáil.
TDs and Senators will be allowed to vote with their conscience, he said.
