Theresa Oswald made the comments as unions and other groups began to prepare for the March 8 NDP leadership vote, where labour organizations could hold one in five delegate slots.
"The NDP in the next year could come up with 50 laws that are terrific for workers and terrific for labour. It doesn't matter a bit if we turn the keys over to Brian Pallister so that he can begin a reign of terror against workers," Oswald said.
"It's critically important that (party members) decide who has the best chance of beating Brian Pallister in the next election. I say with humility that I think that person is me, and the stakes have never been higher."
Oswald has seen very little formal labour support since she helped lead a caucus coup against Premier Greg Selinger last fall. Paul Moist, national head of the Canadian Union of Public Employees accused Oswald and other caucus rebels of "political treason."
The provincial branch of CUPE came out in formal support Monday of Selinger, who is in a three-way leadership race against Oswald and former cabinet colleague Steve Ashton.
"Greg has an excellent track record in Manitoba and I believe he led us to one of our biggest victories yet in 2011," said CUPE Manitoba president Kelly Moist, who is also Paul Moist's daughter.
CUPE members could play a key role in the leadership race. The NDP was still working on official delegate counts Monday, which are based on membership numbers of union locals, constituency associations and other groups. Moist estimated CUPE locals across the province could send more than 250 delegates to the convention. That's more than 10 per cent of the total that are expected.
The United Food and Commercial Workers Union, which expects to have more than 150 delegates, had yet to endorse any of the candidates. Neither had smaller unions such as the United Fire Fighters of Winnipeg.
Oswald promised Monday that if she won, she would allow unions or management to apply for arbitration 45 days after the start of a strike or lockout — down from the current 60 days.
A political analyst said a big part of Oswald's strategy is to try to convince party members that she is the only one who can beat the Tories in the election slated for April 2016.
"It's part of an overall narrative that has surrounded her ever since she first spoke up against (Selinger)," said Royce Koop, who teaches political science at the University of Manitoba.
Oswald has previously used other strong language against the Tories. She has accused them of having an "anti-women, anti-gay" agenda, which the Tories have denied.
"If she has something meaningful to say about our policies or positions we will be happy to comment," read the one-line written response from Tory spokesman Mike Brown to Oswald's latest accusation.