Milk supplies could be under threat this Christmas after pay negotiations broke down at Dairy Farmers’ biggest Queensland plant.

The workers union says Dairy Farmers can’t afford to meet their pay demands because of pressure to supply cheap milk to Coles.

On Christmas Eve, about 90 workers will walk off the job, shutting down distribution at the Crestmead plant for 24 hours.

“It’s not something people are enthused or want to do, but they feel they’ve had no choice and that Dairy Farmers are the Grinch that has stolen Christmas,” said Duncan Pegg from the workers union.

“It could, unfortunately, cause quite significant milk shortages.”

The union says Brisbane workers are paid five per cent less than their Victorian counterparts, and that Dairy Farmers’ management is claiming to be squeezed by supplying cheap milk to Coles.

In a statement issued by Dairy Farmers, it claims to have “put a fair and reasonable offer on the table” to staff.

It also says there would be no disruption to milk supply.

The union has told 7News the company had been training office staff to take over operations during the strike, but says that won’t make up the shortfall.