Prime Minister Justin Trudeau is suggesting electoral reform might not happen after all, despite an election promise that last year's vote would be the last one under the existing system.

And he also suggested there's less need for electoral reform now that the Conservatives are out of power.

Trudeau made the comments in an interview with Quebec newspaper Le Devoir. Speaking in French, he said the Liberal government will only change the first-past-the-post system if Canadians are open to it.

"We're not going to prejudge that it's necessary," Trudeau told Le Devoir.

The prime minister suggested Canadians are happier with the existing system now that Stephen Harper is out of office.

"With the current system, they now have a government with which they're happier. And the need to change the electoral system is less compelling," Trudeau said.

The degree of support needed for electoral change, he added, depends on the size of the change.

"Less support and a small change, that would maybe be acceptable," Trudeau said. "A bigger change, that would take more support."

'A lot of frustration'

Trudeau and Democratic Institutions Minister Maryam Monsef have talked about wanting broad support before going ahead with electoral reform. The question for the government, Trudeau admitted, is what constitutes broad public support.

The government set up a special committee last spring to study electoral reform options, listening to expert witnesses and hearing from Canadians. Liberal officials say the committee heard a range of views during a series of cross-country committee meetings and townhall events.

In question period, NDP Leader Tom Mulcair accused Trudeau of backing away from reform since his party won with the existing system.

"Instead of inventing excuses and backing away from his solemn promise to Canadians, will he work with us in good faith to deliver the fair, proportional electoral system that voters deserve?" Mulcair said.

Trudeau didn't address whether he was backing away from electoral reform, instead accusing Mulcair of reversing his position.

"In the spring, the member opposite was tremendously worried we would use our majority to ram through changes to Canada's electoral system... Now he's changed his mind and he wants us to use our majority to ram through electoral change. Mr. Speaker, saying one thing and then its opposite was exactly what landed that member in that seat in this House," Trudeau said, referring to Mulcair's seat as leader of the third party.

Nathan Cullen, the NDP's democratic reform critic, said Trudeau promised electoral reform during the election one year ago when he needed progressive voters to support him.

"Why make the promise, why back away from it now? Well, because the system that is broken now works for him. That's the only conclusion one can come to. And why did he make the promise in the first place?" Cullen said after question period. "To get elected."

"This is a longstanding policy of the NDP," he added. "This was part of a package to attract particularly progressive voters over, and in large extent it worked."

"The expectation though from Canadians is that he actually follows through on this commitment."

Francis Scarpaleggia, the Liberal MP who chairs the electoral reform committee, said it's a complex issue, with supporters of change proposing several different systems with a number of variations, and that the MPs are going to continue to do their work.

"[Trudeau is] going to take input from the committee, he's going to take input from the minister, he's going to consider what Canadians want, and that will influence the way he approaches this issue," Scarpaleggia said on the way out of the Liberal caucus meeting Wednesday morning.

"He understood that there's a lot of frustration in the country. Many people feel that their votes don't count," he said.

Scarpaleggia says he hopes the committee can reach consensus on some core issues.

"There's a degree of civility and collegiality that I think is exemplary," he said. "There's enough goodwill there that I'm hoping that we're going to get a consensus."