Prime Minister Justin Trudeau has let Canadians down by abandoning his election promise to end the current first-past-the-post voting system, says the president of Fair Vote Canada.

Réal Lavergne, head of the non-profit group that advocates for voting system reform, told Radio-Canada that yesterday's decision to scrap electoral reform was a violation of the prime minister's promise to usher in "open and transparent government."

"We are extremely disappointed. We had high hopes for this government," Lavergne said.​

Fair Vote Canada isn't the only group dismayed by Trudeau's flip-flop.

"The Liberals broke a sacred and simple election promise … in a cynical move to keep winning undeserved majority governments," said Unifor's national president, Jerry Dias, in a release.

The president of Canada's largest private sector union said the decision amounts to the breaking of a "sacred and simple" election promise.

"More than just voting for electoral reform, Canadians wanted an end to political games we have seen coming out of Ottawa for far too long," Dias said. "What they got … instead was just more of the same."

Katelynn Northam, of the electoral advocacy group Leadnow, questioned what Trudeau's U-turn means for other promises made by the prime minister.

"If Trudeau is willing to betray voters on his signature election promise, what does that mean for his other commitments?" Northam said in a statement.

Northam also suggested the current political climate warrants a voting system shakeup — now more than ever.

"A Trump-style candidate could never win over a majority of Canadian voters — but in our broken first-past-the-post system, a hateful candidate could win with as little as 35 per cent of the vote."

Fight not over

Lavergne said young people "appear to be particularly outraged" by the government's electoral reform backtrack. 

And while the Liberal government has ended its plan to make the 2015 election the last using a first-past-the-post system, electoral reform groups say they will continue to push for change.

"The fight for proportional representation isn't over. A majority of Canadians do want electoral reform, and we'll keep fighting until we win," Northam wrote.

Fair Vote Canada organized a protest outside Trudeau's Montreal constituency office Thursday evening. Other demonstrations are planned for Calgary, Toronto and Vancouver. 

Young voters disappointed after Liberals bail on electoral reform7:40