A defeated NDP MP says he does not trust prime minister-designate Justin Trudeau to fulfil his bold promise to reform Canada's electoral system.

"I honestly do not believe that — at the leadership level of the Liberal Party — there is a commitment to proportional representation," Craig Scott said in an interview with Terry Milewski on CBC's Power & Politics.

Scott, who went down to a stunning defeat in Toronto-Danforth, the riding of former NDP leader Jack Layton, penned a "frustrated" Facebook post in the aftermath of his party's defeat.

He called his former Liberal colleagues in the House of Commons "lazy" and "arrogantly waiting for the messiah to take them back to the promised land of power."

Scott said he has reached out to Liberal MPs, individually, to say he shouldn't have used such inflammatory language.

But he maintains that he is genuinely concerned about prime minister-designate Justin Trudeau's commitment to changing the way Canadians vote.

"The question really is whether or not the Liberals … have set something up to fail."

Former NDP MP for Toronto-Danforth Craig Scott, who was defeated in the Oct. 19 election, says he doesn't trust Justin Trudeau and the Liberals to reform Canada's voting system. (Pawel Dwulit/Canadian Press)

"The Liberals did a very good job at making people think they're either open or, in some on-the-ground campaigns, committed to proportional representation," Scott said,

"[In fact] they never, ever, committed to proportional representation."

The Liberal Party did, however, promise in its party platform to strike an all-party parliamentary committee to study electoral reform.

Proportional representation, ranked ballots and electronic and mandatory voting are among the electoral changes that could be "fully and fairly" studied by the committee, the party said.

Trudeau promises end to 1st past the post

The Liberal commitment to change the electoral system dates back to a party policy conference in January 2012.

At the time, party members voted 73 per cent in favour of implementing preferential ballots for all future federal elections.

"Will it help us?" Trudeau said at the time, "Me, I am a fairly polarizing figure, it might actually harm me in my own riding, but I think it is a good thing for Canada that we move towards this," he said.

Throughout the campaign, Trudeau consistently vowed that the general election on Oct. 19 would be the last one using the first-past-the-post voting system.

But Scott said he doesn't trust the party that just won 39.5 per cent of the vote — but a commanding majority of seats in the House of Commons — to actually move forward with a system of proportional representation.