Chanting "keep your promises" and "electoral reform now," around 70 people gathered in front of Calgary-Centre MP Kent Hehr's office Saturday to decry Prime Minister Justin Trudeau's decision not to move forward with a major campaign promise.

Trudeau had promised to do away with the long-standing "first-past-the-post" voting system during the 2015 federal election, but earlier this month announced he is changing course.

He later defended the decision, saying Canada's national unity was more important than the government's commitment to replace its first-past-the-post electoral system.

Bob Dickson said he voted Liberal primarily because he believed the party would reform the voting system and sees the move to drop the key campaign platform as a means of trying to hold onto power.

"If we want true democracy, if we want to take care of our citizens, take care of our people, we have to give the power back to the people, and that includes proportional representation," he said.

Ann Silbernagel said she felt betrayed as she supports the Green Party, but voted Liberal strategically.

"I said, 'if we vote in Trudeau, this will be the last time we have to vote strategically,' and I believed," she said. "I really believed in the progressive platform."

Premier Rachel Notley speaks to reporters after giving a speech in Calgary on Saturday. (Kate Adach/CBC)

Premier Rachel Notley was asked about Trudeau stepping back from the promise after giving a speech in Calgary.

"I think that typically speaking, when you run on a major issue, you're taking a big risk when you walk away from it," she said.

Similar protests were held in cities across the country. In Edmonton, a mock funeral procession was held, with black-clad mourners trailing a bagpiper and carrying a cardboard coffin with the words "RIP Electoral Reform promise."