OTTAWA -- The NDP did not adequately prepare for campaign challenges including the thorny debate on the niqab, according to created in the wake of the party's disappointing 2015 election results.

The issue of face coverings became heated during the last campaign after former Conservative leader Stephen Harper insisted on a ban on the garments at citizenship ceremonies -- a debate that contributed to the plunge in NDP support in their stronghold in Quebec.

New Democrats were not ready to deal with the fallout, according to findings presented by a panel led by NDP president Rebecca Blaikie following discussions with rank-and-file supporters across the country.

"While members are proud of our principled position, many questioned why the campaign was unprepared for the intensity of the debate and lacked a plan to shift campaign coverage back to our offer for Canadians," the report said.

The "principled position" refers to a stance held by NDP Leader Tom Mulcair, who maintained he agreed with the courts that found the Conservative rule unlawful.

Mulcair characterized his position on the niqab as one of the defining moments of his career in his first post-election interview with The Canadian Press.

It was the right thing to stand up to Harper on the issue, Mulcair noted, adding it is always wrong to divide Canadians on questions of race and religion.

"Could a different result have been achieved? Perhaps," he said. "But I wasn't going to do something that I had never done in my career."

There are also supporters who wonder whether Mulcair's strengths were appropriately played up during the campaign, the report noted.

"We heard disappointment from members who felt that discussions about the strategy employed in the debates led to a situation in which our leader's full capabilities -- as demonstrated in the House of Commons over the previous years -- were not on display," it states.

"Across the country, we heard that our party activists did not understand why we refused to participate in some national debates."

The NDP is now the third party in the House of Commons, holding 44 seats -- down from 95 seats in the previous parliament.

The working group also put forward suggestions for the 2019 election, such as calling for a campaign team to be in place two years ahead of the vote.

The report said a campaign strategy needs to be presented to the party's election planning committee a full year before the next election.

The 2015 campaign was an "entirely new experience" for the party because it had never entered a campaign as the official Opposition, nor had it led in the polls for weeks prior to and during the race, the working group observed.

The panel's final report builds on interim findings released in February that noted the NDP's campaign lacked an overarching narrative, instead presenting the party as "cautious change" as opposed to the "real change" the Liberals claimed to offer.

Its release comes ahead of the NDP's convention in Edmonton from April 8-10, where Mulcair will face a critical leadership review to determine whether he will stay at the helm of the party.

Blaikie has suggested 70 per cent is likely the threshold of support needed for Mulcair to keep his job, though the party's constitution only stipulates a leadership race must be held within one year if 50 per cent plus one delegate support it.

Mulcair has been asked repeatedly to provide his number -- the level of support that would prompt him to resign -- but he has refused to spell this out.

"There had been shortcomings in that campaign -- I assume full responsibility for them," he said outside the Commons in February.

"Rebecca is repeating what she's heard across the country, as I have, giving that sort of an idea. But far more importantly, Edmonton is going to be about the party moving forward."