Tom Mulcair says while the NDP suffered some disappointing election losses, it deserves credit for the ousting of Stephen Harper's Conservative government after nearly a decade in power.

"I think the NDP formed the only real opposition Mr. Harper ever had to face and that's one of the reasons we were able to defeat him," the defiant leader of the New Democrats said in French.

Mulcair's comments came after he met with his caucus Wednesday afternoon for the first time since the NDP was reduced to third-party status in the Oct. 19 federal election.

We had set as our number one priority to make sure this was an end to Stephen Harper's Conservatives... Mission accomplished. - Tom Mulcair, NDP leader

He said the NDP, during its four years as the Official Opposition in the House of Commons, successfully exposed the Harper government for its ethical lapses, weak management of the economy and poor environmental record.

"We led the charge against the Harper government," said Mulcair on Wednesday.

Asked if he thought the New Democrats did all of the hard work for the Liberals, Mulcair said the NDP was the "best Official Opposition Ottawa has ever seen."

"We had set as our number 1 priority to make sure this was an end to Stephen Harper's Conservatives, and you know what? Check that box. Mission accomplished," said Mulcair.

Mulcair, who has kept a low profile for the past two weeks, appeared on CBC's This Hour Has 22 Minutes on Tuesday night, where he channeled his inner Drake, dancing to the singer's latest video, Hotline Bling.

22 Minutes tracked him down - dancing to Drake 0:20

Mulcair intends to lead the 'progressive opposition'

Mulcair said he took full responsibility for the NDP's election losses and that a formal review of the campaign would be conducted by NDP president Rebecca Blaikie and national director Anne McGrath.

Defeated Ottawa MP Paul Dewar will also help as he has been appointed to help reorganize the party in the wake of its disappointing election results.

We're just going to pick ourselves up, dust ourselves off and keep going because we know that Canadians want that powerful, progressive voice here in Parliament. - Tom Mulcair, NDP leader

"I assume all of the responsibility as leader of the party, but at the same time we know this is the second best result we've ever had in terms of the number of seats," said Mulcair after meeting with his caucus.

Mulcair said he intends to lead the New Democrats, who have begun to call themselves "the progressive opposition," to victory when the next federal election is called in 2019.

He said he was "extremely confident" party members would place their trust in him because he sensed "strong, positive energy" during today's caucus meeting.

"We are going to be a very constructive, progressive opposition and we're going to make sure the government follows through with their promises."

Mulcair said the NDP's accomplishments include "setting down roots across the country" and that despite the party's election losses, it "got back" three seats in Saskatchewan and "swept Vancouver island."

"We're just going to pick ourselves up, dust ourselves off and keep going because we know that Canadians want that powerful, progressive voice here in Parliament," he said.

Mulcair's fate as leader of the party will be decided when a leadership review is held during the NDP's annual convention in Edmonton in April.

'Larger than expected' cabinet

Mulcair and his 43-member caucus met behind closed doors just as Prime Minister Justin Trudeau addressed the public following the swearing-in of Canada's new cabinet.

"It's clear from the election results that Canadians were ready for change," Mulcair said as he congratulated Trudeau and his cabinet in a news release.

"Today's swearing-in ceremony turns another page on the previous administration. While this change is welcome in Ottawa, progress made in the coming months and years will reveal the strength of that change."

Mulcair said the NDP was "disappointed" that Trudeau's 30-member cabinet was "larger than expected."

"Gender parity in cabinet is a good first step and should be congratulated, but achieving fairness and equality for all Canadians is a long-term goal that requires hard work," Mulcair said.

"I look forward to pressing the new prime minister and his cabinet on their progress."