Marois criticized Coalition Leader Francois Legault for calling on her husband, Claude Blanchet, to testify at a legislature committee.
After being silent on the issue in recent days, Marois spoke out on Tuesday, without any prompting from reporters, and dismissed Legault's call as a desperate political move.
"I'm inviting Mr. Legault to calm down," she said. "Mr. Legault is launching personal attacks and I don't think it's acceptable behaviour for someone who wants to be premier of Quebec and I believe it undermines his credibility."
The controversy erupted after a 2009 wiretap, played recently at the Charbonneau Commission, suggested the then-president of the Quebec Federation of Labour was ready to enlist the aid of the Parti Quebecois to help thwart a corruption probe.
In the recording, now ex-president Michel Arsenault is overheard saying the union has a "deal with Blanchet."
Blanchet had business dealings with the labour federation's Solidarity Fund through a company he owned.
The fund invested just under $3 million with Blanchet's company, BLF Capital. At the time, the company owned a couple of buildings valued at $5 million. The investment lost money over the next few years. Blanchet is no longer involved in the organization.
Arsenault was overheard saying the idea was to use Blanchet to persuade Marois to come out against the idea of holding any corruption inquiry.
Arsenault testified such a conversation never happened and Marois has said the PQ was never asked to stop an inquiry from happening.
Blanchet was the founding president of the fund in 1983. He held the job until 1997.
Blanchet has not spoken publicly about the deal but Marois reiterated Tuesday there was nothing illegal about the deal.
Legault said Blanchet should be made to answer questions about the so-called deal before any future election.
A flurry of financing announcements by the government this week has fuelled speculation Marois will soon call a provincial election.
"It is important that Quebecers know before voting what happened," Legault said, adding there are still plenty of unanswered questions.
Marois invited Legault to look at the Charbonneau Commission's own evidence and documents on her husband. The PQ's lawyer spent more than an hour asking Arsenault questions about the Blanchet deal just last week.
Liberal Leader Philippe Couillard, meanwhile, rejected the idea of having Blanchet appear before a legislature committee.
"While the Charbonneau Commission is sitting, it's not the role of the national assembly to transform into a parallel Charbonneau Commission," Couillard said in Montreal.
"There's one commissioner and she'll decide who she wants to hear from."
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