OTTAWA -- Prime Minister Justin Trudeau is shrugging off concerns about his attorney general attending a private Liberal party fundraiser this week held at a Bay Street law firm that's registered to lobby her.

Justice Minister Jody Wilson-Raybould is the star attraction at Thursday night's $500-a-head, invitation-only soiree at the Torys LLP firm in downtown Toronto.

"Please join us for a private evening in support of the Liberal Party of Canada with the Honourable Jody Wilson-Raybould," says the invitation, a link for which is buried on the Liberal party web site but not searchable for the general public.

Lobbyist registry records show that at least one Torys LLP lawyer is actively registered to lobby Wilson-Raybould on the issue of corporate and mutual fund tax law.

A spokesman for the Liberal party said the event is being "hosted personally by Mitch Frazer, a partner at Torys LLP, not by Torys itself," and that no Torys lawyers registered to lobby the minister will be in attendance.

Braeden Caley added in an email to The Canadian Press that federal conflict of interest and ethics commissioner Mary Dawson cleared Wilson-Raybould's participation in advance.

"As one would expect, all MPs have a role to play in attending events for their political party and the commissioner's office recognized that fundraising is an important part of all MPs' political engagement," Caley wrote.

The ethics commissioner's office did not immediately respond to a request for comment.

Federal conflict-of-interest rules forbid cabinet ministers from soliciting funds from anyone who has lobbied or is likely to lobby the minister's department.

The optics and timing of the Toronto event are problematic for Trudeau's Liberals.

"When the attorney general has a fundraiser for the Liberal party at one of the top law firms in Canada, it blurs the lines between what is Liberal party business and what is government business," Conservative MP John Brassard said in an email.

Ontario Premier Kathleen Wynne has just barred her cabinet members from attending private fundraisers, following embarrassing revelations that ministers were expected to raise up to $500,000 annually for the provincial Liberal party -- a task that often entailed perceived conflicts of interest.

Ontario, like British Columbia, does not limit how much corporations and unions can contribute to party coffers, setting up scenarios in which massive donations coupled with private access to legislators raise a multitude of concerns.

Trudeau, speaking Wednesday in Montreal, said union and corporate donations are forbidden under the rules for federal political parties, while donations by individuals are strictly limited. Canadians can contribute up to $1,525 annually to a registered federal party, plus the same yearly amount to a riding association or candidate, plus another $1,525 to a party leadership contestant.

"The federal government and the Liberal Party of Canada has very, very strict rules around fundraising," said Trudeau.

The prime minister also lauded Wynne's decision to ban her cabinet members from attending private fundraisers, but failed to address the question of whether Wilson-Raybould's event presents a potential conflict of interest.

"There are a number of provinces that still have work to do in terms of demonstrating public trust and I think banning union and corporate donations, as we have done at the federal level, is an important step that different provinces should consider," said Trudeau.

At a later stop in Trois-Rivieres, Que., the prime minister offered that he's "always open to discussing further improvements with other parties and other levels of government."

NDP ethics critic Alexandre Boulerice said this week's fundraiser "raises serious ethical concerns" because it offers access to a minister in exchange for a donation.

Boulerice said the Liberals are developing a "bad habit" of cash for access, citing a recent offer for partisan donors to win a trip with Trudeau to Washington and another for donors to win dinner with Finance Minister Bill Morneau.

Boulerice said he finds it problematic that the federal ethics commissioner is providing a green light.

"We have a bigger problem," said Boulerice. "The rules themselves should be tightened."

Liberals themselves once took a dim view of such potential conflicts -- when they were in opposition.

"This kind of event clearly crosses the line," Ralph Goodale, the party's deputy leader at the time, said in January 2014 when it was revealed Conservative heritage minister Shelley Glover attended a Winnipeg fundraiser that included stakeholders from the arts community.

"It is improper, and quite frankly the donation should be paid back."

Glover ended up not accepting the donations.