Fortescue Metals Group says WA's safety regulator has no legal basis to ask for documents relating to sexual harassment at three of its mine sites, and it will not be pushed into releasing the private information of staff.

The mining giant was yesterday charged with 34 counts of refusing or failing to supply documents to a WorkSafe inspector within a specified time, without a reasonable excuse.

But in a statement this afternoon, a Fortescue spokesperson said the company had been working constructively with WorkSafe over a six-month period, and had repeatedly asked for the legal basis for requesting those documents, but none was provided.

"We will not be pushed into breaking the law or releasing the private information of our team mates without their knowledge and consent," the spokesperson said.

"There is no legal basis for the regulator to demand this information so we are understandably very cautious when asked to release private and personal records.

"We have never refused to comply."

WorkSafe has declined to comment further on the matter. 

Robust processes in place: FMG

The Fortescue spokesperson said "sexual harassment, bullying and misconduct has no place at Fortescue".

"We take our responsibility to provide a safe and respectful workplace for all our team members very seriously."

They said the company had "robust processes" for people to raise concerns.

"All reported cases are thoroughly investigated and, where substantiated, we take swift action to address any behaviour that is not acceptable to Fortescue or in the community which has included termination," the statement read.

WorkSafe yesterday said the documents related to cases of alleged sexual harassment at three Pilbara iron ore mining operations but did not say how many victims and offenders were involved, nor when the alleged incidents happened.

The company has not yet entered pleas to the charges, but if found guilty could face a cumulative penalty up to $1.87 million.

Before Fortescue issued its statement questioning the legal basis of WorkSafe's requests, Premier Mark McGowan said he was limited in what he could say because the matter was before the courts.

"But we did toughen the laws to require companies to be more forthcoming and stronger in their actions in this regard … and obviously the laws we put in place are working," he said.

"I'm not going to pre-empt it [the court proceedings], anything I say can be used in court proceedings, but all I'd say is you need to have a very strong approach to these issues in the workplace, and that's what we support and that's what our laws support."