A Conservative decision to name two cabinet members to an advisory panel that will vet Supreme Court candidates could undermine the independence of the selection process, say opposition MPs.

Public Works Minister Christian Paradis and Diane Ablonczy, secretary of state for small business, are slated to serve as the two Tories on the five-member committee that will hold its first meeting Tuesday.

But both the NDP and the Bloc Québécois say people who owe their jobs to Prime Minister Stephen Harper should have no role in the deliberations.

"This committee, as envisioned, was to provide parliamentary and independent advice to the prime minister," said New Democrat justice critic Joe Comartin.

"If it's cabinet people on it, the suspicion has to be that they're not there providing independent [advice], they're just there as mouthpieces for the Prime Minister's Office."

Comartin has an additional reason for objecting to Paradis. He is one of 67 Tory candidates whose names have come up in connection with the so-called in-and-out election financing controversy under investigation by another Commons committee, as well as by Elections Canada.

Real Menard, the Bloc justice critic, said that, as a matter of principle, no cabinet members should be involved in the judicial vetting process.

"We have to respect the separation between judicial power and the government," said Menard. "I hope the government will realize [they made] a terrible mistake."

Menard plans to introduce a motion when the committee meets Tuesday calling on the Tories to find two new members.

Dominic LeBlanc, the Liberal member of the committee, couldn't immediately be reached for comment. But he's expected to meet Tuesday with his NDP and Bloc counterparts to try to map out a common opposition strategy in the dispute.

The Tories, for their part, have been adamant that they're free to name whomever they want to the panel.

"Ultimately, the appointment of a Supreme Court justice is a function of the executive," said Justice Minister Rob Nicholson.

"We've put this process in place and we have the right to name some individuals.… We're not providing a veto to the Bloc or the NDP on these things."

Constitution gives PM job of naming judges

At issue is the choice of a new judge to replace Michel Bastarache of New Brunswick, who has had heart trouble and stepped down at the end of the court's spring term in June.

Under the Constitution, appointments to the Supreme Court are the sole responsibility of the prime minister. But the former Liberal government set up an a vetting panel to help fill the previous vacancy on the bench.

That committee, which included representatives of the legal community as well as MPs, came up with a short list of three candidates just before the 2006 election. Harper inherited the list when he took office and chose Justice Marshall Rothstein, who was born in Manitoba and has a judicial record considered moderately right of centre.

Nicholson announced last spring that the Tories would establish another advisory panel to help fill the Bastarache vacancy, but limited the members to sitting MPs.

The justice minister will provide the panel with a confidential list of names when it sits Tuesday. It's not known how many candidates there will be, but the expectation has been somewhere from five to eight.

The committee will work behind closed doors to narrow the list to three, from which Harper will make the final choice. The winner will also appear before a separate Commons committee to field questions in public, but unlike similar hearings in the United States, the Canadian MPs won't have any veto power.

The composition of the preliminary vetting panel isn't the only hot-button issue at play in the process.

All three opposition parties are pressing the Tories to ensure the new judge will be fluently bilingual. Bastarache was known as a champion of minority language rights who often took the lead in court decisions on that sensitive subject.