Strike action at a key Coles warehouse will have a significant impact on the availability of products including beer, toilet paper and toothpaste at Victorian supermarkets, according to reports.
About 600 workers are striking and say they are prepared to continue as long as it takes to resolve their complaints over pay and conditions, which they say are inferior to all other Coles warehouse workers.
National Union of Workers state secretary Tim Kennedy told the Herald Sun that imported beer brands including Heinekin, Corona and Becks could be affected.
"I think you will see an impact at about the six-day mark, there could be empty shelves," Mr Kennedy told the newspaper.
"If they do run out of beer then they will probably start talking to us."
Mr Kennedy said Coles had spent millions of dollars trying to get around the strike action by sending supply lines through other warehouses.
But he said the 600-worker warehouse was Coles' national distribution centre and so the strike would seriously undermine the company's capacity to stock its shelves.
"Most consumers will not take the risk to go to a Coles supermarket now in the belief that things may not be there," Mr Kennedy told reporters at the warehouse.
"They'll probably go to the competition, so it will have a significant effect on sales for Coles."
The strike began at 6am (AEST) on Tuesday at the Somerton warehouse in Melbourne's north.
About 300 workers are braving the rain in red union waterproof ponchos and huddling around fire barrels outside the warehouse gates.
Storeman Shane Weston said workers were not angry but upset about not receiving the same shift penalties and conditions as at other Coles warehouse sites and said workers were prepared to stick together and strike for as long as it took to resolve their claims.
The union said it was set to speak with Toll management which manages workforce issues at the site later on Tuesday.
Toll spokesman Christopher Whitefield said the company had offered a four per cent pay rise, higher than deals negotiated by the union at similar work sites.
"In order to keep attracting and retaining the best people, Toll will continue to balance the needs of the business to remain competitive within the industry," Mr Whitefield said in a statement.
Mr Whitefield said less than half of the 600 workers at Somerton endorsed the industrial action.