By Ethan Lou

TORONTO (Reuters) - Canada will change the way it fills vacancies on its top court, letting qualified lawyers and judges nominate themselves for Supreme Court openings and using a nonpartisan advisory board to recommend candidates, Prime Minister Justin Trudeau said on Tuesday.

There is a looming vacancy on the nine-member Supreme Court, with Justice Thomas Cromwell announcing he will retire in September, giving Trudeau his first chance to appoint a member of the court since becoming prime minister last November.

Under the current system, Supreme Court justices in Canada are effectively picked directly by the prime minister, who does not require parliamentary approval. In the United States, by contrast, Senate confirmation is required for U.S. Supreme Court appointments.

The change in Canada, announced in a government press release, creates a new system for determining candidates for the court, where justices serve until the age of 75.

Once potential justices have applied, and a shortlist is compiled by the advisory board, the justice minister will consult other levels of government, various parliamentary committees and opposition politicians. The eventual nominee, picked by the prime minister, will appear in a question-and-answer session before legislators from all parties.

The move by Canada's Liberal government is aimed at making selection more transparent, Trudeau wrote in a column in the Globe and Mail newspaper on Tuesday.

"The process used to appoint Supreme Court justices is opaque, outdated, and in need of an overhaul," Trudeau wrote.

There is excitement in legal circles about the new process, and the open nominations have the potential to improve diversity, said Canadian Bar Association past president and spokeswoman Michele Hollins.

"You may reduce the risk that the people involved in the process, however well-meaning, will seek out the people that they know," she said.

But advocacy group Democracy Watch said the process is still partisan because the prime minister has the final say.

While the selection of Supreme Court judges in Canada has traditionally been less political than in the United States, there have been controversies. In 2014, the Supreme Court rejected then-Prime Minister Stephen Harper's pick of Marc Nadon in a high-profile clash, saying Nadon was not qualified.

Trudeau said the independent and nonpartisan advisory board will be chaired by former Progressive Conservative Prime Minister Kim Campbell.

U.S. Supreme Court appointments have become highly politicized. The nine-member U.S. high court has had a vacancy since the death of a justice in February because the Republican-led Senate has refused to take any action on Democratic President Barack Obama's nominee to the position.

(Reporting by Ethan Lou in Toronto; editing by Jeffrey Hodgson, Will Dunham and Andrew Hay)