The decision to strip Julie Snyder's access to the credit is aimed at creating a level playing field for all players in the independent television production industry, Couillard said Tuesday.
He accused the previous PQ government of creating an unfair situation by changing the criteria for Snyder's company, which is called Productions J.
The firm is closely tied to television network TVA, which is a major client for her company's offerings and is owned by Peladeau's Quebecor Inc (QBR.B).
Snyder said she's weighing legal action, suggesting the Liberals are acting out of spite because she's engaged to the perceived front-runner in the PQ race.
The popular producer and host, who is a household name in Quebec, says the survival of Productions J is at risk because hundreds of thousands of dollars are at stake.
Couillard denied Snyder's claims of discrimination and sexism, saying the goal was "to harmonize things and make things equal."
"We know that independent producers have a very different challenge from a producer who is linked to a broadcaster," he told a news conference.
In an interview with Le Devoir, Snyder rejected the government's line of thinking, reaffirming her company's independence from Quebecor.
Peladeau reminded reporters that Snyder's career in television has spanned a quarter-century and began long before they became a couple.
The PQ leadership hopeful didn't want to weigh in further.
"I don't know the motivations of the Liberal government," Peladeau said.
The PQ's Nicolas Marceau, who was finance minister when the rules were changed in the last days of that government, reiterated Tuesday that the previous situation was unjust and discriminatory.
Under those now reinstated rules, production houses tied to television networks were not allowed to collect the credit.
Marceau said a businesswoman should not be penalized for being in a relationship with a particular partner, especially in 2015.
"I don't believe in the bedroom test," Marceau said.
He said Snyder's company had qualified for the tax credit between 1998 and 2008, before the Liberals yanked it.
Marceau could not say whether other companies were in the same situation as Snyder's but he denied playing favourites in awarding Productions J the tax credit.
Instead, he defended the PQ move as righting a wrong.
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