Maintenance workers are paid 21 per cent less at Saputo Dairy Australia's Burnie plant than at the company's "sister sites" on the mainland, a union says.
The Australian Manufacturing Workers' Union says production workers at the site are also paid much less than mainland counterparts, with a union official putting that gap at 40 per cent.
Maintenance workers at the dairy giant's Burnie cheese processing plant walked off the job on April 23.
The AMWU said the workers were calling for fairness.
"We are over being the poor cousin here in Tasmania," AMWU state organiser Mike Wickham said.
"We shouldn't be paid less than the mainland.
"This is unacceptable."
Mr Wickham said the Burnie workers were more skilled and the site was more technical than mainland counterparts, but the workers just wanted to be paid like their mainland colleagues.
"What's good on the mainland is good for Tasmania," Mr Wickham said.
"There's no argument Tasmanians should earn less than their mainland counterparts."
Saputo said: "Saputo Dairy Australia is committed to continuing negotiations in good faith to reach an agreement for our valued maintenance workers at our Burnie manufacturing site."
The company did not dispute the union's 21 per cent pay gap claim about maintenance workers.
Canadian-headquartered Saputo completed a $280 million acquisition of Lion's speciality cheese business in 2019.
The union movement is becoming increasingly vocal about the pay gap between Tasmania and the mainland in various businesses and sectors.
"Workers will not want to come to Tasmania, nor will they want to stay, if they can obtain better working conditions, higher salaries and job satisfaction elsewhere," Unions Tasmania said in its submission for the upcoming state budget.
The AMWU said it was asking Saputo for pay parity between the Burnie workers and their mainland counterparts.
The union said that had been ignored during enterprise bargaining negotiations.
"Workers on sister sites in Victoria earn 21 per cent more than their colleagues in Burnie," the AMWU said.
"The cost of living is impacting Tasmanians as workers struggle with prohibitively high house prices and soaring rents."
Saputo last year announced a $20 million investment in its Smithton plant.