The 2009 exchange, which was played at the Charbonneu Commission, is between two senior union bosses — then-federation president Michel Arsenault and Jean Lavallee, a former president of the federation's construction wing.
Arsenault is overheard saying he has a deal with "Blanchet," a reference to Claude Blanchet, Marois' husband, who previously ran the Quebec Federation of Labour's billion-dollar Solidarity Fund.
Arsenault also said in the conversation he'll "talk to Pauline" to make sure the PQ didn't support holding a public inquiry that would focus on unions.
At time of the recorded call, the PQ was the official Opposition.
Arsenault states that the governing Liberals were not fully onboard with an inquiry looking at unions, even as public pressure mounted to have a wide-ranging probe into revelations about organized crime in the labour federation.
The union president was confident the PQ would also dismiss the idea of such an inquiry.
"The PQ won't touch this, I'll talk to Pauline," says Arsenault.
Lavallee, who continued his testimony at the commission on Tuesday, was overheard on the same recording saying a sit-down with "our PQ friends" was necessary.
He testified that no such meeting ever took place and that he knew nothing of the aforementioned deal with Blanchet.
Marois was in Davos, Switzerland, on Tuesday for the World Economic Forum and did not meet with reporters.
Bernard Drainville, a senior PQ minister, brushed off the contents of the conversation between Lavallee and Arsenault.
The PQ was a staunch supporter of a public inquiry into the construction industry while Jean Charest's Liberals balked at such an inquiry before finally agreeing to call it.
Under Marois, the PQ actually extended the Charbonneau Commission's mandate by another 18 months.
"The PQ asked for the commission for three years, I don't know how many hundreds of times we stood up during question period to ask for the commission," Drainville said in Quebec City.
"If there are those who tried to stop us from asking for a commission, they hit a wall of integrity because we asked for it and asked for it often."
The Liberals argued Tuesday that Marois needs to explain the comments.
"Madame Marois herself should come before the media and give her version of what has been said," said Leader Philippe Couillard.
"It's very troubling that...there might have been a deal of a financial nature mixed with the political process.
"If the political process has been altered, this is a very serious allegation."
The Quebec Federation of Labour was firmly opposed to an inquiry before finally changing its tune.
Lavallee said he was against the creation of a corruption inquiry, adding he isn't happy with the hit his reputation has taken after devoting 40 years to the labour movement.
"I'm here and I've been convicted already," Lavallee said. "A public inquiry doesn't help anyone."
Lavallee, who quit the union in 2008 after 27 years as construction-wing president, said he is a PQ supporter and that his wife worked for the party for 10 years.
He said he donated regularly to the PQ until 2008.
The labour federation has been under the microscope at the corruption inquiry in recent months as the probe looks at how organized crime infiltrated it through its construction wing.
For his part, Lavallee has admitted he pushed for certain projects to get financing from the union's investment wing. He has also admitted to having cosy ties with construction entrepreneur Tony Accurso, having vacationed on his yacht a half-dozen times.
Arsenault, who left his post as union president late last year, is expected to testify before the inquiry. He lost a legal fight to stop the wiretap conversations featuring him from being heard by the commission.