A UNION has splashed thousands of dollars on a national advertising campaign to call out a mining giant over what it claims is a "dodgy" move against miners.

CFMEU Mining and Energy will today launch its bold national campaign "Cheap move from the Big Australian", targeting BHP's new in-house labour hire subsidiary, known as Operations Services.

The campaign claims BHP is dishonestly offering BHP jobs to coal miners through Operations Services but BHP describes it as "a new team within BHP that will provide production and maintenance services".

The CFMEU campaign claims workers hired to work on BHP sites by Operations Services "wear BHP uniforms, perform the same tasks as their BHP employees, but are paid 40 (per cent) less".

It also claims they miss out on important working conditions like accident pay and can be transferred to any site in Australia as decided by the company. But BHP's website states Operations Services offers permanent employment opportunities and a range of benefits.

"By creating permanent jobs, we are able to offer our team members security in their employment and income, as well as access to benefits such as sick (personal) and annual leave," the website said.

It also said Operations Services employees had access to market competitive salaries under specific OS terms and conditions and benefits including 9.5 per cent super, generous parental leave benefits, annual leave, personal leave and flexible work options.

Operations Services is recruiting across BHP's coal mines in the Bowen Basin, including Goonyella Riverside, Broadmeadow, Daunia, Peak Downs, Saraji, Blackwater, Caval Ridge, Poitrel and South Walker Creek.

CFMEU Mining and Energy Queensland District president Stephen Smyth argued Operations Services did not employ workers under existing industrial agreements.

"People deserve to know what BHP is doing and the reality of the jobs they are advertising," Mr Smyth said.

"BHP have led the destructive casual outsourcing charge and now they've found an even trickier way to drive down wages by outsourcing jobs to themselves."

"We stand with all BHP workers, whether permanent, labour hire or Operations Services. They do a tough job and produce a valuable, high-quality product - we'll fight for the fair pay and conditions they deserve."

Mr Smyth said the CFMEU's membership base was in support of the "Cheap move from the Big Australian" campaign.

The campaign will involve ads running across television, print and social and digital media.