As a member of the National Assembly in Quebec under the Liberal government of Jean Charest, Mulcair credited the success of England's economy under Thatcher's Conservative Party to the "winds of liberty and liberalism" that "swept across the markets in England."
Mulcair made the comments in April 2001 in the context of a parliamentary commission where he sought to discredit the interventionist tendencies of a separatist government led by Bernard Landry.
"A government should never pretend it can replace the private market. It does not work," Mulcair said in 2001. "It didn't work in England. Up until Thatcher's time, that's what they tried, the government stuck its nose everywhere."
On Wednesday, Mulcair defended his comments as an example of good public administration.
'Good services' a priority for Mulcair
"My No. 1 priority is to get good services to the public," Mulcair said during an afternoon campaign stop in Surrey, B.C., on Wednesday.
"That hasn't changed and that's what that statement was about. Making sure that the public gets the best services possible."
The video post came a week after one of Quebec's largest and sovereigntist-leaning labour federations dropped its long-standing endorsement of the federal Bloc Québécois, with some of its members shifting their support to the NDP.
Mulcair said the news made him "extremely proud" and that he would work hard to keep the support of such unions as the Quebec Federation of Labour.
Mulcair was quick to add on Wednesday that his priorities also include reducing inequality and increase opportunities. "That's what I've always worked towards and that's what I'll continue to work for."
The 30-second clip was unearthed by a Quebec blogger covering the federal campaign and shared on social media on Tuesday by Jean-François Lisée, a member of the Quebec National Assembly for the separatist Parti Québécois.
"When Tom Mulcair cited Thatcher as an example to denounce social-democratic policies!," Lisée said in a post on Twitter pointing to the video and blog post. "Astonishing read," he said.
Mulcair's comments were shared widely but whether they were deemed to help or or hurt him, depends on who you ask.
Others wondered what the unions who support Mulcair's New Democrats would have to say about his admiration for Thatcher's policies.
Some did not see Mulcair's comments as a liability.
Mulcair resigned from Jean Charest's Liberal cabinet in 2006.
A year later, he was elected in a byelection as an NDP MP in the riding of Outremont.
In 2012, he won the leadership of the party.
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