SDLP leader McDonnell sparks outrage over remarks on DUP and Sinn Fein
Fragile political relations at Stormont have taken a further nosedive after the SDLP leader accused the DUP of not wanting to work with Catholics.
Alasdair McDonnell also claimed Sinn Fein "can't tell the truth" about the IRA.
He was recorded by the North Belfast News at the opening of a new constituency office.
The controversial comments were made as a week of intensive cross party negotiations to save the ailing Assembly finished.
Dr McDonnell said: "The DUP don't want partnership - they don't want a taig (derogatory term for about the place. I'm sorry, it's as brutal as that."
The DUP has robustly rejected allegations of sectarianism.
MP Jeffrey Donaldson hit back, saying the SDLP leader was "rabble rousing".
He said: "Not only would we reject the allegations that Alasdair McDonnell has made, we would challenge him with sectarianism. To use a deeply offensive term such as 'taig' in a speech is beneath contempt and demeans the office that he holds as leader of the SDLP.
"Instead of rabble rousing in North Belfast, he would do well to be at Stormont with the rest of the political parties to resolve the issues."
The political institutions at Stormont, which were already under threat over financial difficulties, have been rocked by the murder of IRA man Kevin McGuigan last month.
The father of nine was gunned down in front of his wife in the staunchly republican Short Strand area in what police believe was a revenge attack for the shooting of one-time IRA associate and former commander Gerard "Jock" Davison three months earlier.
Police said they believe individual members of the IRA were involved in Mr McGuigan's murder, piling pressure on Sinn Fein to explain how the supposedly defunct terror group still exists.
Sinn Fein has insisted the IRA has gone away.
However, Dr McDonnell added: "Sinn Fein can't tell the truth. They just can't tell the truth, and they can tell us whatever they like and you've examples like Gerry Adams was never in the IRA and you've examples like Martin McGuinness saying this, that and the other thing. They're not telling the truth."
South Belfast MLA Alex Maskey said the SDLP leader was exploiting the murders for political gain.
He said: "The brutal murders of both Gerard Davison and Kevin McGuigan have been exploited by the unionist parties for their own internal electoral intentions, and Alasdair McDonnell's scurrilous allegations are clearly an attempt to move the SDLP onto the same ground to score cheap political points.
"Sinn Fein has repeatedly challenged the SDLP to either put up or shut up, and if Alasdair McDonnell or any other member of the SDLP has any information on the murders of Gerard Davison or Kevin McGuigan, then they should bring that to the police."
Dr McDonnell has not yet fully explained his remarks, but in a statement to the BBC he claimed that DUP Acting First Minister Arlene Foster had been disrespectful to nationalists in a recent interview.
Ms Foster has temporarily replaced Peter Robinson while the talks process takes place. She was the only DUP minister to stay in the Executive amid the crisis, describing her role as a "gatekeeper" against the possibility of decisions being taken by "rogue" or "renegade" ministers.