Alasdair McDonnell and Martin McGuinness had a heated row at Stormont on Monday in which the SDLP leader used bad language, several sources have told the News Letter.
The angry exchanges took place as the leaders of the Executive parties met to discuss the implementation of December’s Stormont House Agreement.
Around 15 people were at the meeting.
It is understood that the disagreement began after Mr McGuinness challenged the SDLP leader over his party’s stance on welfare reform.
Mr McGuinness has publicly accused the SDLP of going back on December’s deal by tabling a series of amendments to the Welfare Reform Bill.
A Sinn Fein spokesman said that Mr McGuinness would not comment on what went on at a private meeting.
An SDLP spokesman said that the meeting was confidential so it could not comment on what had taken place.
Two Stormont sources claimed that Dr McDonnell had sworn several times while locking horns with the Deputy First Minister, but another source said that he had only once used bad language.
And one person familiar with the clash said that it involved “forthright” views from Dr McDonnell but “wasn’t nasty”.
The individual said that the Deputy First Minister had denied saying some of the things which he said in his recent article for the Belfast Telegraph in which he attacked the SDLP for bringing forward amendments without having “agreed” them with the other Executive parties.
The source added: “McGuinness tried to have a go at McDonnell, but McDonnell wasn’t in the mood for taking it from him.”