The decision to pursue strategic voting in the next federal election was taken unanimously at a weekend meeting of Unifor's national council. Ironically, the gathering featured a keynote speech by NDP Leader Tom Mulcair, who announced his plan to reinstate a minimum wage for workers in federally regulated sectors, rising to $15 per hour over four years.

NDP labour critic Alexandre Boulerice conceded Unifor's decision is disappointing.

"Frankly, I would have preferred clear support for the NDP as the real choice for the next election," Boulerice said Thursday.

Still, he said most labour unions are solidly behind the NDP and it's no surprise Unifor is not among them, given its history of strategic voting. Unifor was formed last year from a merger of the Canadian Auto Workers and the Communications, Energy and Paperworkers unions.

The CAW endorsed Paul Martin's Liberals in the 2006 election in a failed bid to prevent Harper from becoming prime minister.

Dias acknowledged the labour movement has no stronger political ally than the NDP. But while Justin Trudeau's Liberals are less supportive of unions than the NDP, he said he doubts they're intent on destroying the movement, as he believes Harper's Conservatives are determined to do.

"So, if my choice is Stephen Harper or Justin Trudeau, then that's a no-brainer."

Dias said anti-union measures are "red meat" that Harper throws out to pacify "right-wing extremists" in the Conservative party.

He pointed to government and Conservative private members' bills which labour advocates complain would impose unfair financial transparency rules on unions, gut public service collective bargaining and make it harder for federally regulated workers to join a union while making it easier to decertify a union.

Unifor's refusal to unequivocally back the New Democrats in the Ontario election prompted more than 600 federal NDP parliamentary staffers, who are members of Unifor, to look for another union to represent them.

Anthony Salloum, president of the Unifor local that represents the staffers, said members will vote early next month to choose a new union home. They have three options: the United Steelworkers, the United Food and Commercial Workers or the International Association of Machinists.

All three "have indicated full support for the NDP," Salloum said.

By Joan Bryden, The Canadian Press