Labour leader Pat Rabbitte has ruled out joining a coalition government in the Republic with Sinn Féin until the Provisional IRA is disbanded.
Speaking exclusively to the Irish News, Mr Rabbitte, who succeeded Ruairi Quinn as party leader, also claimed that Sinn Féin had so far failed to prove its mettle as a political party in the Republic.
He accused Gerry Adams's party of "pitching its tent" at the protest vote while failing to work on concrete policies for the south.
"It tends to go with every populist demand that there is around the place and merely, in some of the most disadvantaged communities, being seen to be agin everything – that's the Sinn Féin profile," he said.
Mr Rabbitte's party has been rocked by Sinn Féin's success in last year's general election, which saw convicted gun-runner Martin Ferris take a seat from former Labour leader Dick Spring in North Kerry.
Sinn Féin is also increasing its profile on the ground in the working class areas of Dublin, Cork and other southern towns and cities.
Mr Rabbitte dismissed any possibility of his party sitting in government with Sinn Féin in the foreseeable future, saying that such a move "depends on Sinn Féin's willingness to make the final step into the democratic arena"' by disbanding the Provisional IRA.
"Labour has consistently articulated that until such time as Sinn Féin feels able to make that final commitment, that the prospect of a formal coalition arrangement is not on," he added.
He also called on republicans to end the training and recruitment of paramilitaries, the gathering of intelligence and the ending of so-called 'punishment' beatings "because they're anti-democratic".
Mr Rabbitte, who recently paid a one-day visit to Belfast during which he met representatives from all the main political parties, played down the current crisis in the peace process.
"'If you didn't know Northern Ireland well and if you didn't understand Northern Ireland politics you might come away with the view that everything was hopelessly logjammed. But I don't think that's the reality of it.
"I think the parties in Northern Ireland are already in election mode and are jostling for advantage and therefore you have to read between the lines. You then come to the conclusion that the one thing they're all committed to is ensuring that the house of cards doesn't come tumbling down and that they will make the institutions work. I would be hopeful that within the next two months there will be considerable progress."
Mr Rabbitte said he believed that the Good Friday Agreement remained the "best hope" for a lasting peace in the north.
"We have to end the uncertainty about some parties' response to working the Belfast agreement. I would hope that people will realise that before the opportunity comes to vote in May and that we get the institutions back up and running again," he added.
