Former union boss Michel Arsenault is explaining his "deal" with the husband of Quebec Premier Pauline Marois aimed at thwarting the calling of a public inquiry into corruption.

Arsenault says he had an idea in 2009 to speak to Claude Blanchet, Marois's husband, who had business dealings with the Quebec Federation of Labour's (FTQ's) Solidarity Fund through a company he owned.

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Quebec Premier Pauline Marois says she never discussed her husband's business affairs with anyone. (CBC News)

Arsenault told the Charbonneau Commission today he was simply "brainstorming" in a 2009 wiretapped conversation between him and a fellow union executive. They were seeking political alliances to support the FTQ's position that a inquiry was unnecessary.

He thought the business partnership with Blanchet could help them persuade Marois, who was leader of the Opposition at the time, to come out against the creation of an inquiry into corruption in the construction industry.

He said he ended up not calling Blanchet, who had been a director at the Solidarity Fund between 1983 and 1997.

Arsenault told the inquiry that a longtime political attaché at the union told him a day after the wiretapped conversation it would be a terrible idea to get in touch with Blanchet.

Arsenault says he regrets ever bringing up the idea.