A total 140 workers at Lactalis' Bendigo plant began indefinite strike action on Thursday morning.

All the site's production workers halted work from midnight, for an indefinite strike, calling for pay parity with workers in other regions.

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United Workers Union organiser Tom Czech said Bendigo Lactalis workers wanted better pay and job security for themselves, their families and the community.

Mr Czech said Lactalis had a high rate of workers on insecure contracts, such as casual or fixed term contracts for years.

He said called for a "fair and reasonable" pay rise, saying Bendigo workers were paid less than those at Lactalis sites in other regions.

"We have essential workers that are making a stand for a fair wage increase and secure job sin order to support the Bendigo community," Mr Czech said.

"We know that when we have secure jobs we have a strong community and ...that benefits everyone."

The United Workers Union said members were fighting for a wage that reflected their role as essential workers and started to close the pay gap with other Lactalis workers.

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It said workers were also fighting for secure, long-term jobs in Bendigo.

UWU called for a commitment from Lactalis that if it left the Bendigo site, the factory would not be "mothballed" but open to expressions of interest from other dairy operators.

It said workers in Bendigo were saying no, and standing up for their community.

Mr Czech said workers wanted for a fair wage increase after keeping up work through the COVID-19 lockdown to make sure there was fresh milk products on supermarket shelves.

"Lactalis has form when it comes to playing one group of workers off another," Mr Czech said.

"Workers ... have heard threats many times that the company will shut Bendigo if their wages are the same or higher than other Lactalis workers.

"But workers are sick of the threats and want to close the gap of wage disparity with other sites owned by the same company."

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Bendigo worker and UWU delegate David Bish said workers wanted a commitment from Lactalis that diary jobs would continue, even if it left Bendigo.

"If they do shut us down, we want to know they will let this site live again if another dairy company wants to take it on," Mr Bish said.

"There are generations of families that have worked at this site, raised families, contributed to this town. There are farmers that rely on this site to get their milk processed.

"If Lactalis wants to walk away from that, fine - but don't ruin our future in the process. That's the commitment we are seeking."

The union warned that several large dairy operators had "mothballed" sites in the past decades, refusing to sell to other companies to prevent competition.

"This type of industrial sabotage is devastating for regional towns and the dairy industry - with hundreds of good secure jobs leaving the town and companies walking away from the communities that built their brands into the globally celebrated fresh milk products that make companies profitable," the union said.

Pauls Milk custard and sour cream, Farmhouse and Farmhouse Gold premium brands, Ice Break ice coffee, Zymil lactose free milk, Vaalia Yoghurt and Macro organics are among the products made at Lactalis Bendigo.

Lactalis has been contacted for comment.

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