The Perth Mint is considering a ban on all clothing containing metal, including underwire bras, in a bid to boost security.

The mint processes high value precious metal products within its refining and manufacturing facilities.

It recently undertook a security review after a series of breaches, including an incident several months ago in which a contractor working at the refinery allegedly stole a gold bar worth more than $50,000.

A spokeswoman for the Perth Mint said the review highlighted the need to enforce metal-free clothing for any staff, contractors or visitors entering high-security zones. It is a move the organisation is considering.

"One area currently being explored with staff is the use of metal-free clothing for transiting through security checkpoints," the spokeswoman said.

"This will eliminate any question that staff may have precious metal on their person as they exit high security areas.

"The general public visiting the mint will not be affected."

Another option for staff being considered is to change out of their regular clothes at the end of the day.

They could then be scanned separately by a more sophisticated machine which can distinguish between precious metals and zips, buttons and underwire.

"Some of the pieces of precious metal are very, very small so there is a possibility for people to be able to put a small piece of metal underneath a bra strap or behind a metal button," human resources manager Jane King said.

Ms King said there were concerns scanners that could detect the metals while staff were wearing their clothes, such as those used at some airports, could impact their health.

'It's a disgrace,' says union

While a ban on particular items of clothing is yet to be imposed, the Australian Manufacturing Workers' Union said it had been in contact with a number of female staff who have been told by their employer they may have to wear work-issued undergarments.

AMWU state secretary Steve McCartney said the union met with the company last week to raise concerns that such a rule unfairly targeted women and would be an unreasonable imposition.

"We think it's a disgrace," Mr McCartney said.

"It's without any real science behind it and without any real discussion.

"They've got machinery at airports that people can walk through that can tell you what you've had for breakfast.

"I'm pretty sure they could find the technology that excludes women from having to go through this embarrassment.

"We think it's an attack on women's rights and an attack on women."

The Perth Mint said new security technology was being considered, including body scanning equipment.