Mulcair, who intends to step down in fall 2017 when a successor is named, said he plans to work with his parliamentary team to take on the Liberal government when the House of Commons resumes sitting next week.
"I couldn't be more honoured and humbled by the support of our caucus today," Mulcair said.
NDP Leader Tom Mulcair addresses members of his caucus at the beginning of their meeting Sept. 14, 2016 in Montreal. (Photo: Paul Chiasson/CP)
The leader — flatly rejected as the party's long-term chief during a spring vote by rank-and-file members — has recently been fending off an internal push to oust him.
During a speech on Wednesday morning, Mulcair refused to address a push by some members of caucus who want him removed immediately, as opposed to when a successor is named next year.
"My only adversaries in politics are the Liberals sitting across from me in the House of Commons," Mulcair said.
Before the Montreal meeting, multiple current and former MPs — who spoke to The Canadian Press on condition on anonymity for fear of openly criticizing the leader — said they wanted him out immediately.
"My only adversaries in politics are the Liberals sitting across from me in the House of Commons."
No formal vote took place Wednesday on Mulcair's leadership, said NDP caucus chair Charlie Angus, who acknowledged the party's base has been frustrated following a disastrous October election.
He insisted changes will be made.
"We've been a little lost ... we've been trying to find our sea legs," Angus said. "We know that. So, for us, this meeting was about kicking our butts and saying 'Come on, there are a lot of people who are out there who are waiting for us."'
The party has been plagued by sliding poll numbers, shrinking fundraising figures and low morale.
So far, there are no official candidates to replace Mulcair.
It is important for the party to be united and give Mulcair a unanimous show of support as the party prepares to return to the House, said B.C. New Democrat MP Don Davies.
'It is a challenging time'
"It is a challenging time," Davies said. "It is a year after the election and I don't think we are where we would like to be ... when you're lower in the polls, there's naturally people who are agitating for some change and those are important people to listen to."
The NDP's real job is to focus on holding the Liberals to account for the many promises they made in the last election, Davies added.
During the fall sitting of Parliament, the NDP plans to challenge the Liberal government on issues including climate change, health-care funding and indigenous affairs.
NDP to push on C-51
It intends to push for the repeal of Bill C-51, a controversial piece of anti-terrorism legislation passed by the previous government.
The Liberals have promised to amend the law, but New Democrats accuse the Trudeau government of moving too slowly on planned reforms.
"They promised that they were going to take out the most offensive parts of Bill C-51, they haven't done it and we are the only ones who are going to be holding them to account," Mulcair said.
It is challenging to pounce on the Trudeau Liberals during the first year of their mandate because Canadians want to give the benefit of the doubt to a fresh face, Mulcair said.
"We've been through this before," Mulcair said during a morning speech to caucus. "But we have to believe that Canadians are going to start to take notice a little more this time.
"We've been through this before when Liberals steal our platform, steal our ideas ... pretend they are on the left."
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