SINN Féin's John Finucane has been criticised for continuing his work as a solicitor despite being elected as an MP.
Mr Finucane has joined his client Carl Frampton in the High Court several times this week for the boxer's legal action against his former manager Barry McGuigan.
The case is expected to last for two weeks.
Mr Finucane works up to 20 hours a week for his law firm, according to his Westminster register of interests.
The North Belfast MP amended the register in July following Irish News queries as it previously suggested he still worked full-time for Finucane Toner.
Mr Finucane ousted Brexiteer DUP deputy leader Nigel Dodds in last December's election, benefitting from added pro-Remain support after the SDLP and Greens stood aside.
Sinn Féin MPs do not take their seats at Westminster due to the party's abstentionist policy.
UUP Newtownabbey councillor Robert Foster said that seeing Mr Finucane represent clients while not taking his seat "adds insult to injury".
"The people of North Belfast face many problems and challenges. It is bad enough that they have an MP who refuses to attend Westminster and represent them by speaking up for them in the chamber of the House of Commons, but to see him representing clients in a Belfast court merely adds insult to injury," he said.
Sinn Féin did not respond to requests for a comment.
The party has previously said Mr Finucane is "focused on his role as an MP" and has "taken a back seat in the day-to-day work" of his law firm.
