The Ontario Public Service Employees Union alleges the LCBO has classified retail employees it says commonly work 25 to 40 hours a week as "casual" workers who are paid less and have fewer benefits than full-time staff.
The union says in its claim against the LCBO and the province that 70 per cent of the casual workers are women, many of whom have worked for the liquor chain for more than a decade — something it alleges amounts to anti-female discrimination.
LCBO spokeswoman Heather MacGregor says the complaint is unfounded, adding the majority of full-time retail employees are also women.
She says the LCBO pays women and men the same salaries as agreed to in collective bargaining, and will challenge the union's claims at the tribunal.
The 7,000 LCBO employees represented by OPSEU have threatened to walk off the job next Friday unless a contract with the liquor seller is reached before May 17.
The head of the union said the retailer has long refused to deal with the alleged wage disparity.
"The LCBO has been a jewel in the Ontario Crown," OPSEU President Smokey Thomas said in a release.
"The corporation and the government that controls it have been lauded for their success. And now they will be held accountable for their shame."
MacGregor said the way the LCBO pays its workers is similar to that of other companies.
"We pay differently based on the nature of the work itself, but that's consistent with what most retailers in Ontario do in any event. There is no discrimination based on sex," she said.
MacGregor said the LCBO expects contract talks to continue non-stop until the deadline.