Quebec Justice Minister Simon Jolin-Barrette is facing an investigation by the national assembly's Ethics Commissioner after he appointed his friend to become a judge earlier this month.

Commissioner Ariane Mignolet announced Monday she had opened an inquiry after receiving a complaint from Liberal MNA Monsef Derraji, who alleged the justice minister violated the code of ethics and professional conduct of the national assembly.

Derraji alleged that the appointment "raises ethical questions about the role of the Minister in the final phase of the appointment process."

On May 4, Jolin-Barrette appointed his friend, Charles-Olivier Gosselin, to the Court of Quebec. The close personal relationship between the two men was first reported by Le Soleil, which noted the justice minister had also officiated the wedding of Gosselin and his spouse in Sillery, Que. on May 15, 2015.

The national assembly appoints the Ethics Commissioner, an independent authority, to ensure members and their staff follow the code of ethics and conduct.

Since the relationship was publicized last week, Jolin-Barrette and Quebec Premier François Legault defended the controversial appointment.

"We reiterate that the process, which is strictly governed by the Courts of Justice Act and the Regulation respecting the procedure for the selection of candidates for the office of judge, was followed and respected in every respect. The Ethics Commissioner can count on my full cooperation," the justice minister told The Canadian Press on Monday.

His office also recalled last week that an independent selection committee — not the Minister of Justice — recommends the top three candidates for a judicial appointment. The justice minister then makes their choice and submits it to the council of ministers, which has to confirm the appointment.

But on Sunday, he admitted he would declare a conflict of interest to the council of ministers if he had to appoint the judge again. He also told reporters that he is open to changing the rules regarding judicial appointments. 

During a visit to Sherbrooke, Que., last Friday, Legault, who said he learned about the personal relationship through the media, told reporters there was no conflict of interest. He also said the rules allow a friend to be appointed as a judge.

"This is not a conflict of interest," he said in a press scrum. "How can we talk about a conflict of interest from the moment the people are chosen by an independent committee?"

Opposition parties in the national assembly all say the appointment of a friend to such a position raises serious ethical questions.

With files from The Canadian Press