Australia Post is employing unskilled workers on 457 visa holders to deliver parcels and sort mail, according to a union, which says they are being used to drive down the postal service's costs.

The Communication Workers Union says Australia Post is one of many large companies deliberately turning a blind eye to contractors employing overseas workers on the visas.

Driving down postal service costs: Australia Post is said to be deliberately turning a blind eye to contractors employing overseas workers on visas. Credit:Justin McManus

''It's just cheap, unregulated labour that does not comply with minimum wages,'' the union's Victorian state secretary Joan Doyle said.

Ms Doyle will meet Workplace Relations Minister Bill Shorten on Friday to discuss what she says is the growing use of 457 visas by contractors for Australia Post.