The SDLP has suspended the whip from Newry and Armagh MLA Justin McNulty.
Mr McNulty attended the first sitting of the NI Assembly on Saturday but left before proceedings ended
The party said the MLA, who is manager of the Wexford Gaelic football team, “left today’s sitting of the Assembly without seeking permission and did not return for important parliamentary business which included the SDLP taking up its role as the official opposition at Stormont”.
The All-Ireland winning footballer was present at Stormont when the assembly met to appoint a new power-sharing government but left during proceedings.
It later emerged he had driven to Co Wexford for a Division 4 Allianz National Football League game, which Laois won by 1-19 to 0-12.
Mr McNulty was appointed manager of Laois last October and there had been tensions with his party over his ability to juggle both roles.
Within hours of the whip being suspended, Mr McNulty’s picture was removed from the list of SDLP MLAs on the party’s website.
An SDLP spokesperson said: “All SDLP MLAs were informed by the party’s chief whip that attendance at today’s sitting was mandatory for the duration of the Assembly proceedings.
“This was a historic day that saw the restoration of devolved government, the election of the first nationalist first minister and leader of the opposition. People rightly expect their elected representatives to be there for work.
“We expected all members of our team to be there to support their colleagues. Accordingly, as Mr McNulty was not in his place, did not seek the permission for his absence and breached the direct instruction of the whip, the SDLP chief whip has suspended the whip with immediate effect.”
Mr McNulty has so far declined to comment.