Prime Minister Justin Trudeau is accusing the Conservatives of launching "horrific, partisan attacks" on former governor general David Johnston.
Trudeau delivered a full-throated defence of Johnston on Friday after tapping him this week to serve as special rapporteur on foreign interference.
The Conservatives say Johnston is too close to Trudeau, while the Bloc Québécois allege he has been "chummy" with China.
Both opposition parties, along with the NDP, have called for a public inquiry in to the allegations of foreign meddling in the last two federal elections.
Speaking at an event in Guelph, Ont., Trudeau sidestepped questions about his own relationship with Johnston.
He instead defended the former governor general, who was appointed to that role on the recommendation of Conservative prime minister Stephen Harper, as a Canadian of the highest integrity.
"David Johnston has served this country in many, many different ways through a long and unimpeachable career," Trudeau said.
Johnston's appointment came after Global News and the Globe and Mail newspaper reported allegations of Chinese interference in the 2019 and 2021 federal elections.
If the Liberals had been hoping the appointment would put a lid on the partisan fighting that has surrounded the allegations, that hasn't been the case.
Conservative Leader Pierre Poilievre has criticized Trudeau for appointing someone he once described as a "family friend," while noting the former viceregal is also a member of the Pierre Elliott Trudeau Foundation.
The foundation, which supports mentorship programs for aspiring scholars and leaders, has figured prominently in the Tories' allegations about links between Trudeau and China.
Trudeau did not specifically address his personal relationship with Johnston or the rapporteur's role on the foundation bearing his father's name when asked by reporters.
The prime minister accused the Conservatives of being more concerned with scoring political points than defending Canada's democracy.
"There is no better name than David Johnston, which makes it so astonishing, but also so clarifying, to see the Conservative party simply not interested in actually getting answers," Trudeau said.
"They are engaging in horrific partisan attacks against a man of extraordinary integrity."
In a statement to The Canadian Press, Johnston described attempts to undermine the country's democracy as "serious matters."
He said he was "privileged" to have accepted the appointment as special rapporteur and was finalizing the details around his role.
"I will work with officials to finalize the mandate, which will be made public promptly, to look into foreign interference in the last two federal general elections," he said, "and make appropriate recommendations on how to further protect our democracy and uphold Canadians' confidence in it."