Media playback is unsupported on your device Media caption The float at Montreal's Fête Nationale parade

A video from a Montreal festival parade has gone viral with critics suggesting it shows the event's lack of diversity.

The clip shows a singer on a float pushed by four black men in khakis, as a white crowd dances around them in the Canadian city.

The video uploaded on Facebook was captioned (in French): "I'm not sure the organisers of the parade understood the concept of diversity."

The organisers called the outcry "unjust" and "exaggerated".

Saint Jean Baptiste Day, known as Fête Nationale or National Holiday, is marked throughout the Quebec province every 24 June, as a celebration of Francophone history and culture.

The Montreal event was themed on Quebec's history.

Maxime Laporte, president of the Société de St-Jean Baptiste de Montréal, told the CBC news network that it was a coincidence black men were pushing the float.

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The volunteers had been recruited from two local organisations: the Association for School Retention and the the Louis-Joseph-Papineau High School Sports Team.

"We need to look at this situation as a whole," Mr Laporte said. "It was a wonderful parade that represented [Montreal's] diversity. People need to make a better judgment call in these circumstances."

Local resident Félix Brouillet shot the video, which has been shared more than 12,000 times, attracting many outraged comments.

The Association of Muslims and Arabs for Secularism in Quebec also complained that it saw only black people - plus a couple of Asians and Arabs - pushing the floats.

"What do we say to the black child who is happy to go and celebrate the national holiday?" it asked on Facebook.

However, school football coach Steve Lubin, who knows some of the students participating parade, told CBC he thought the issue was overblown.

"When kids work hard, I don't see colour. I see participants. It just so happens that my kids were working hard and that white people happened to be sitting on the float. If it was the opposite, would we be having this discussion? I'm not so sure."

In statement on the festival's Facebook page, the organisers said the parade's eco-friendly vehicles were not motorised and so had to be pushed along.

"It goes without saying that these young people - who were proud to participate in the event - were not chosen according to the colour of their skin," it said.

They say it was their most diverse Fête Nationale to date.