After weeks of criticism and controversy in the House of Commons, the Liberal government has agreed to support an NDP proposal that gives no one party a majority of seats on the committee that will study electoral reform.

At the NDP's suggestion, seats on the committee would be allotted proportionally according to the popular vote in last year's federal election. The 12-member committee would be composed of five Liberals, three Conservatives, two New Democrats, one member of the Bloc Québécois and Green MP Elizabeth May.

The Liberal proposal would have based the committee, like all other committees of the House of Commons, on the current seat count, with six Liberals, three Conservatives and one New Democrat (the Liberals also proposed that one member of the Bloc and May could have non-voting seats on the committee).

"We heard the opposition's concerns that we were perhaps behaving in a way that was resembling more the previous government than the kind of approach and tone that we promised throughout the electoral campaign," Prime Minister Justin Trudeau explained later on Thursday.

"We're happy to demonstrate that absolutely we're looking for ways to better work with our colleagues in the House, to better hear from Canadians and their concerns and I look forward to working towards reforming our electoral system with the input of as many Canadians, including opposition parties, as possible."

Interim Conservative Leader Rona Ambrose nonetheless blasted the Liberal government for not committing to a referendum.

"The voting system actually does not belong to the Liberals and it does not belong to the NDP; it belongs to Canadians," she said during question period. "When we change what their vote means, Canadians get to say yes or no."

Maryam Monsef, minister of democratic institutions, moved amendments to the NDP motion, but agreed with the NDP's proposal for dividing committee seats.

During Question Period Opposition leader Rona Ambrose calls PM Justin Trudeau's stance on not holding an electoral reform referendum "one of the most arrogant and elitist things" that she's ever heard. 3:08

"Today is about co-operation," Monsef told reporters afterwards. "The impetus for all of this is to get the conversation beyond one on process and towards the committee beginning its work of hearing from Canadians. That is the motive for all of this."

NDP critic Nathan Cullen said his side was "very pleased" with the latest developments.

"If the process is seen as, and is, fair and trusted by Canadians, then it greatly improves the chances that the result will be fair and trusted by Canadians," he said "The government has agreed with us today that no one party should have the power to unilaterally push through changes to our voting system."

Minister of Democratic Institutions Maryam Monsef discusses the decision to support the NDP proposed structure for the electoral reform committee. 8:17

The Liberals had been criticized for trying to give themselves a majority of the committee's seats, essentially basing the committee on the first-past-the-post voting system that the government is committed to replacing.

"When the minister presented the Liberal model it was soundly rejected ... just because it looked like the deck was stacked," Cullen said.

Cullen publicly suggested the NDP's preferred design in February, but the Liberals did not show interest and instead tabled their own proposal last month, before backing down today.

Speaking after Cullen and Monsef, Conservative critic Scott Reid signalled the Official Opposition would not be supporting the amended motion. The Conservatives insist that a national referendum be held before the electoral system is changed.

Reid later described the agreement between the New Democrats and Liberals as a "backroom deal" and said he was not consulted beforehand. He added that he was "mighty ticked off" with the turn of events.

"Support of one other party or indeed of every other party is not a replacement for the people," Reid told reporters. "What's being proposed today is, in my opinion, wildly undemocratic and quite frankly if it leads to the kind of changes the prime minister has favoured all along it will be unconstitutional."

Reid has suggested that the Liberals prefer moving to a ranked ballot, a system that has been projected to benefit the Liberals.

MPs Mark Holland, Scott Reid, Nathan Cullen and Elizabeth May discuss the electoral reform process. 16:58

In response to questions from reporters, Monsef did not completely rule out the possibility of a referendum.

"Today is about taking that first step and beginning to shift that conversation from process to hearing from Canadians. The final step will be determining what the buy-in of Canadians that we have reached out to broadly will be. And I'm looking forward to the committee's recommendations on that."