Rio Tinto says worker shortages contributed to a decision to boost the number of driverless trucks at its WA iron ore mines from ten to 150.

The trucks will be used at the company's Pilbara mine sites, controlled remotely from its operation centre in Perth, 1,500 kilometres away.

Rio Tinto says the purchase makes it the owner of the largest fleet of driverless trucks in the world.

Spokesman James Petty says the technology is necessary to meet the company's targets.

"Now we're pulling people from the likes of Perth and the east coast; we're flying people from the east coast as well," Mr Petty said.

"There won't be enough people to be able to run all the trucks that we need to run.

"And it's not just us; our competitors in the Pilbara are growing at the same sort of rates that we are."

The secretary of the Construction, Forestry, Mining and Energy union, Gary Wood, isn't convinced.

"The issue there is very clear; it's in the wording," Mr Wood said.

"It won't mean job losses but it will be the loss of job creation for Australian workers."