More than 1400 Victorian dairy workers will walk off the job to fight for better pay and conditions.
The processing workers from dairy giants Saputo, Fonterra, Peters and Lactalis will strike for 48 hours from Wednesday.
The United Workers Union says the companies have refused to offer fair wages and improved working conditions amid rising living costs.
"Workers don't make this decision lightly," national secretary Tim Kennedy said.
"They're not even asking for a wage increase that matches inflation, just five per cent or so that gets them a little closer to being able to keep up with skyrocketing costs."
The sites affected include Saputo's Allansford, Cobram, Leongatha and Kiewa factories and Laverton's Integrated Logistics Centre.
The strike action comes as the Australian Competition and Consumer Commission continues to deliberate over Coles acquisition of two Saputo processing plants.
Fonterra workers at Cobden, Darnum and Stanhope sites will take industrial action, along with staff at Peters Mulgrave and Lactalis, Longwarry.
Along with the wage increase, workers want personal leave accommodating their 12-hour shift pattern and community service leave for helping in natural disasters.
The union has acknowledged the industrial action will lead to disruptions for the dairy sector.
But Mr Kennedy said the dairy companies were vital to many regional Victorian communities, so the strike was necessary.
"This is more than a wage tug-of-war," he said.
"It's about safeguarding the heartbeat of our regional communities."
Fonterra director Rob Howell said the company had a "fair and reasonable offer" on the table for workers, with a minimum 10.5 per cent salary increase over three years and more leave options.
Fonterra would ensure there were minimal disruptions from the industrial action, he said.
"Our farmers will continue milking and we will be doing everything we can to ensure that their precious, perishable milk can be collected and not wasted," Mr Howell told AAP in a statement.
"We are confident that the supply of our dairy products will continue during the industrial action."
Saputo, Peters and Lactalis have been approached for comment.
Australian Associated Press
