Singh said some of the people behind the demonstration are pushing "false information" through "inflammatory, divisive and hateful comments."

GoFundMe records show Singh's brother-in-law, Jodhveer Singh Dhaliwal, donated $13,000 to the group behind the demonstration — dubbed the "freedom convoy" by participants.

In a statement sent to CBC News, Singh said he doesn't support a campaign that harbours "extremist and dangerous views" and "unequivocally" disapproves of his brother-in-law's decision to donate.

'Dangerous and divisive rhetoric'

"[I] ... disagree with him about this donation and told him so. I am against this convoy and against the dangerous and divisive rhetoric we're seeing coming from it," Singh said.

"I understand people are frustrated that we're still in this pandemic two years later. The best way to get out of this pandemic, and to keep ourselves, our families and our communities safe, is to get vaccinated and to listen to public health experts."

An NDP source, speaking on background, said Dhaliwal didn't fully comprehend what the money would be used for.

"There was a misunderstanding. Once he understood the true nature of this organization, a process was started to return the donation," the source said.

While he waits for GoFundMe to process the reversal, Dhaliwal has hidden his name from the public list of donors to the convoy, the source said.

The protest is being organized by Canada Unity, a group that opposes COVID-19-related measures. Its organizers say it is intended to push Prime Minister Justin Trudeau and his government to drop the vaccine mandate for truckers and do away with other public health protections.

Trudeau responded today by saying the vast majority of Canadians disagree with the convoy's message. He pointed out that Canadian truckers have a vaccination rate of approximately 90 per cent.

"The small fringe minority of people who are on their way to Ottawa, or who are holding unacceptable views that they're expressing, do not represent the views of Canadians who have been there for each other," Trudeau told a news conference today.

WATCH | Trudeau says protesting truckers represent fringe minority of Canadians

In Canada Unity's "memorandum of understanding," convoy organizers call on Ottawa and the provincial and territorial governments to do away with what they call "unconstitutional, discriminatory and segregating actions and human rights violations" brought about through programs like the vaccine passport system for non-essential businesses and vaccine requirements for public servants and transport workers.

The group demands that government leaders either make the changes or "RESIGN their lawful positions of authority Immediately."

Singh condemned Conservative politicians for backing people opposed to public health measures.

"While not surprising, it is disturbing that Conservative MPs are supporting this convoy," he said.

 Conservative deputy leader Candice Bergen is the latest Conservative MP to come out in support of the convoy protest. (Adrian Wyld/The Canadian Press)

Candice Bergen, deputy leader of the Conservative Party, added her name to a growing list of MPs who say they stand with the protesting truckers. She said her party opposes all federal vaccine mandates.

Bergen said Trudeau's attempt to boost vaccination rates through new mandates has "dealt our already crumbling supply chain another blow." She said the policy will exacerbate an existing trucker shortage and "drive inflation higher than it's been in over 30 years."

"Now more than ever, our economy needs to be reopened, and we need every sector working in order to recover from the pandemic. I support peaceful demonstrations against these mandates, and our truckers from Portage-Lisgar and from across Canada," Bergen said, referring to the riding she represents.

Supporters of truck drivers protesting the COVID-19 vaccine mandate cheer on a convoy of trucks on their way to Ottawa on the Trans-Canada west of Winnipeg on January 25, 2022. (David Lipnowski/The Canadian Press)

Conservative finance critic Pierre Poilievre and Garnett Genuis, a Conservative MP from Alberta, have called the federal policy a "vaccine vendetta."

In an interview with CBC News, Poilievre accused Trudeau and Singh of "insulting" truckers taking part in the convoy.

"You don't have to agree with the everything that every trucker says, but you can, for God's sakes ... thank the truckers for keeping us alive and acknowledge their legitimate frustration," he said.

WATCH | Pierre Poilievre says he supports peaceful protesters taking part in trucker convoy 

Martin Shields, a Conservative MP who represents the Alberta riding of Bow River, has said it's time to put an end to the "Trudeau Liberal government's mandates and freedom-curbing restrictions." Shields has promised to meet with the convoy when it arrives in Ottawa.

Bob Benzen, the Conservative MP for Calgary Heritage, said he supports the convoy and its protest against "coercive, intrusive and authoritarian dictates of this Trudeau government."

"This vaccine mandate for truckers who served us over two years of the crisis is ridiculous and unacceptable," Benzen said.

Conservative Leader Erin O'Toole has been less vocal than some of his caucus colleagues regarding the convoy protest. Speaking to reporters on Monday, O'Toole accused Trudeau of "dividing Canadians" by pushing shots on truckers — but was non-committal when asked if he'd meet with convoy organizers when they arrive in the nation's capital.

"It's not for the leader of the opposition or a political party to attend a protest on the Hill or a convoy. It's up to politicians to advocate for solutions in a cost of living crisis in a way that's responsible and respectful of the public health crisis we are in," he said.

While the vast majority of cross-border truckers have had the necessary shots, industry groups estimate as many as 12,000 to 16,000 unvaccinated Canadian drivers could be pulled off the road because of this policy.

Various business groups — including the Canadian Chamber of Commerce, the Retail Council of Canada and the Canadian Manufacturing Coalition — have expressed concerns about the trucker mandate.

In a statement Wednesday, the Canadian Federation of Independent Business (CFIB) urged the federal government to drop its mandate "before supply shortages and price increases drive even more businesses to the brink."

Experts agree that while the new mandate is likely to disrupt the flow of goods, the recent pandemic wave driven by the Omicron variant, COVID-19 restrictions in China and a global shortage of shipping containers are also to blame for ongoing supply issues in the food and retail sectors.

Transport Minister Omar Alghabra pushed back against Conservative claims that the vaccine mandate is causing higher prices and empty shelves.

WATCH: Transport Minister Omar Alghabra discusses timing of vaccine mandate