The Australian Manufacturing Workers' Union says mining equipment manufacturer Caterpillar has laid off up to 50 workers at its operation in Tasmania.

Union state secretary John Short said the workers will be cut loose from the company's manufacturing plant in Burnie.

"It's a pretty mean-spirited act to lay off workers on the eve of Christmas," Mr Short said in a statement.

"It will take the merriness out of the family time meant to be enjoyed for these workers.

"The dedicated and skilled workers here in Burnie deserve better than this."

Mr Short said the company had started building machinery at a new plant in Thailand.

"When you add in job lay-offs before Christmas and the commencement of operations in new premises in Thailand, I think workers and the Burnie community have every right to know what Caterpillar's real plans are," he said.

Caterpillar did not immediately respond to AAP's inquiry.