Union members flooded the streets of Toronto in a spirited Labour Day celebration emboldened by the birth of the country's biggest union for private-sector workers.

Thousands of workers stretched for more than 12 blocks Monday in a parade peppered with steel drum bands and labour flags and banners from more than a dozen unions.

Front and centre in their red union T-shirts were members of Canada's newest labour group, Unifor, formed this weekend from a merger between the Canadian Auto Workers and Communication, Energy and Paperworkers unions.

Unifor national president Jerry Dias called the boisterous march a symbolic start for the group as it launches an ambitious campaign to draw in members from precarious and traditionally non-union jobs.

"Today is really about opportunity, it's about hope. It's about us saying we've had it and it's about us saying we're determined to change the direction of the country," said Dias.

Union membership has declined in recent years, though it saw a slight uptick to 31.5 per cent last year, according to Statistics Canada. The public sector makes up the vast majority of union employees.

Dias, a lifelong union member who was endorsed by the former heads of the CAW and CEP, was elected Saturday with about 87 per cent support at Unifor's founding convention in Toronto.

Unifor currently represents some 300,000 workers.

NDP Leader Thomas Mulcair, who was among a small contingent of New Democrat marchers, said Unifor will help solidify the base of the Canadian labour movement at a time when middle-class jobs are under attack.

"We've seen a stabilization in the labour movement after several years of decrease. Stephen Harper is encouraging a lot of people to get back involved in the labour movement," Mulcair said.

"The Conservative party has been pushing down wages and working conditions for women and men across the country" through the expansion of the temporary foreign workers program, while manufacturing job losses are also taking a toll, he said.

Marcher Paul Dolgov, an actor, said joining a union has provided him with valuable protection on the job.

"The union provides us with a fair working environment. We get nice wages... basically it's one of the best places to work and we are protected."