The woman who is the Liberal government's pick for commissioner of official languages is trying to persuade the Senate, which Prime Minister Justin Trudeau is turning into a chamber of non-partisans, that her own partisanship should not disqualify her from becoming an independent officer of Parliament.

Madeleine Meilleur, a long-time Ontario Liberal MPP who served in a variety of cabinet posts, including attorney-general and minister responsible for francophone affairs, faced a tough grilling by senators who asked her how she could effectively do the job amid concerns about her Liberal ties.

Both the Senate and the House of Commons must approve Ms. Meilleur's appointment.

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The senators are expected to vote on it later this week and the outcome is far from certain.

Serge Joyal, a member of the independent Liberal caucus in the Senate, began by pointing out that he knows Ms. Meilleur well and has crossed paths with her many times.

But even Mr. Joyal raised concerns about whether she could be impartial.

"You are now going to be trusted with a position, a role, which provides advice to a government which you are tied to in a number of different ways," Mr. Joyal told Ms. Meilleur.

"I don't think you've really been accorded time to give yourself distance from these ties to truly convince us today that you can, in fact, exercise your responsibilities in full autonomy and independence."

Ms. Meilleur replied that there is no disputing that she was actively involved in politics for many years.

But during that time, she said, "I defended and fought for Franco-Ontarians among my peers who were not always in agreement with me."

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Throughout the session, Ms. Meilleur maintained that she is a francophone first and a politician second and that she could be counted upon to act independently when it comes to protecting French-language rights.

The 38 Conservatives will likely oppose Ms. Meilleur's appointment. There is no telling what the 42 independents and non-affiliated senators will do. And even the so-called independent Liberals cannot be counted upon for their approval.

On Monday, the Acadian Society of New Brunswick said it will apply for a judicial review of Ms. Meilleur's appointment with the Federal Court.

"We are convinced that the nomination process was flawed, the opposition parties were not consulted and also we believe strongly that Madame Meilleur was advantaged by her proximity to the Liberal Party," Kevin Arseneau, the society's president, said in a telephone interview.

Ms. Meilleur has said that, before she stepped down as an MPP, she considered applying to become a senator, but was told that recent politicians are not wanted in the Red Chamber because they are deemed to be too partisan.

Both the Tories and the NDP have complained about the Liberal background of Ms. Meilleur, who donated to the Liberals and to Mr. Trudeau's leadership campaign.

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She also met with key members of Mr. Trudeau's staff as she was making inquiries about the language commissioner's job.

In the House of Commons on Monday, the Prime Minister rose to defend his government's choice to succeed former languages commissioner Graham Fraser, saying "we will not hold against any qualified candidate their background in politics."

Heritage Minister Mélanie Joly was repeatedly forced to defend the selection of Ms. Meilleur.

"There were 72 candidates that participated in the process," Ms. Joly said.

"An independent firm went through all. Ten of them went through testing, and also there were reference checks done. In the end, because of the great expertise and experience of Madeleine Meilleur, she was clearly the best qualified candidate to become the official languages commissioner."

Last week, The Globe and Mail reported that three members of Ms. Joly's staff worked for the Ontario Liberals while Ms. Meilleur was in office, with two of them reporting directly to Ms. Meilleur.

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Ms. Joly said her employees, which include her director of communications and scheduling assistant, had nothing to do with Ms. Meilleur's appointment, and a "clear firewall" was set up between her office and the selection committee.