The Trudeau government will face increasing pressure to hold a referendum on changes to Canada's voting system with a special parliamentary committee set to make the recommendation in a report released on Thursday.

Two sources tell The Globe and Mail the all-party committee, on which opposition MPs have a majority, will recommend a referendum on electoral reform, with an option to keep the status quo. Other options will be left open to include forms of proportional representation, the sources said.

The Liberals promised during last year's federal-election campaign that the election would be the last under the first-past-the-post system, which ensures the candidate with the most votes in an electoral district wins, even if he or she doesn't win a majority.

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An opposition source said the majority report will call for a referendum, "while leaving some leeway to the government in terms of the question."

The source said the Liberal members of the committee are expected to issue a minority report.

"They have shown no signs of endorsing a referendum," the source said.

Democratic Institutions Minister Maryam Monsef has repeatedly said she finds referendums divisive and doesn't think they are the best approach to public policy. However, she has also said her government will not move forward on electoral reform without "broad consensus" from the public, casting doubt on her government's commitment to keeping its campaign promise.

A senior government source said the committee's report is one factor in the government's decision; the process also includes town halls by members of Parliament, Ms. Monsef's own national tour and an upcoming federal-government online survey. It is not expected cabinet will make a decision on electoral reform until early next year.

"It's not over," the government source said.

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NDP leader Tom Mulcair asked Prime Minister Justin Trudeau point blank in Question Period on Wednesday whether 2015 will be the last election under the current system. "Yes or no?" Mr. Mulcair asked.

"We made a commitment to ensure that 2015 would be the last election under first-past-the-post," Mr. Trudeau said. "That is why we are working with parties across the House and Canadians across this country to figure out how to best improve our electoral system. There is a broad range of opinions out there."

Mr. Trudeau said he looked forward to the committee's report and the upcoming consultations.

"I encourage Canadians to look to their mailboxes next week and participate in the national survey so we can hear their views on electoral reform," he said.

Ruby Sahota, one of five Liberals on the 12-member committee, told The Globe this week the committee heard from many organizations that advocated for proportional representation.

But she also said many other witnesses didn't want a referendum "because they felt it was a mechanism that would not allow for change."

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"I think you'll find a lot of consensus will come out of the committee," Ms. Sahota said.

NDP MP Nathan Cullen, vice-chair of the electoral reform committee, accused Ms. Monsef this week of undermining the committee's work by publicly saying she has not heard consensus on electoral reform. "If the minister feels like this consensus doesn't exist, show me the proof," he said.

Conservative MP Scott Reid, also vice-chair, declined to speak with The Globe before the report is released.