Liberal Leader Justin Trudeau made a rare public tribute to his father, former prime minister Pierre Elliott Trudeau, during Monday night's Munk debate on foreign policy in Toronto.

The comments followed NDP Leader Tom Mulcair's comparison of anti-terror Bill C-51 to Pierre Trudeau's invocation of the War Measures Act during the 1970 October Crisis.

"Both of these gentlemen have at various points attacked my father. Let me say this very clearly. I am incredibly proud to be Pierre Elliott Trudeau's son," the Liberal leader said.

"I know that he wouldn't want us to be fighting the battles of the past. He'd want us squarely focused on the future, and how we're going to respond to Canadians' needs."

This brief — and rare — tribute to his father elicited sustained applause from the audience at Roy Thomson Hall.

Pierre Elliot Trudeau died 15 years ago today. His son wore a black tie to the debate, forgoing his usual Liberal red, to mark the anniversary.

"I'm sorry to hear that Mr. Trudeau thinks we are talking about his father in a negative way," Mulcair replied. "I am talking about historical fact, that the only party who stood up in 1970 and defended rights and freedoms was the NDP."

Several commentators on Twitter expressed some shock at Trudeau's use of his father's name, especially in the context of the War Measures Act, one of the elder Trudeau's most infamous and controversial moves during his time as prime minister.

Whoa. Trudeau plays the Dad Card. —@acoyne

This is the first time Trudeau has owned his father's legacy in this explicit a way. That I am aware of. —@mdentandt

Is that the most Trudeau has talked about his father during the campaign? <a href="https://twitter.com/hashtag/munkdebate?src=hash">#munkdebate</a> —@aradwanski