(Adds details on Rio Tinto, Fortescue, union submissions)

MELBOURNE, Aug 20 (Reuters) – Sexual harassment is rife at mining camps in Western Australia, with firms across the industry reporting multiple complaints that have led to 48 staff being fired by the world's biggest, BHP, since 2019, submissions to a government inquiry showed.

The inquiry was initiated after high-profile cases of sexual assault by miners in the mineral-rich state emerged this year, and as the sector struggles with a dire skills shortage and a low proportion of female staff.

Submissions to the investigation were made public this week, including a survey by The Western Mine Workers' Alliance, a union representing hundreds of workers in Pilbara, a region rich in the iron ore that is Australia's most valuable export.

The survey of 425 workers showed two-thirds of female respondents had experienced verbal sexual harassment while working in the FIFO mining industry, and 36% of women and 10% of men some form of harassment in the last 12 months.

"We have heard detailed reports from members about supervisors and managers pressuring female workers into sexual activity in order to access training and job opportunities and there is a widespread perception that such activity takes place," said the union, which is calling for an independent body to investigate complaints.

"I have seen a man watch porn on bus and plane. I have found a porn magazine in a truck. I have had underwear stolen. I have had a male try get into my room… I reported harassment on numerous occasions and nothing was done," the union quoted an unnamed woman who works at Rio Tinto as saying.

A Rio spokesperson pointed Reuters to its submissions for examples of steps it is taking as part of an industry-wide response that includes improving safety and reporting procedures and mining camp infrastructure and tightening policies around alcohol.

In more detailed accounts to the panel, which will make recommendations to West Australia's parliament in April 2022, BHP said it had fired 48 workers in two years for incidents related to sexual harassment.

It said it received four rape allegations, one of attempted rape, other reports of unwanted sexual touching, and 73 substantiated reports of sexual harassment from June 2019 to June 2021.

It said it was spending $300 million to increase camp security, improving workforce training, vetting practices and making reporting of incidents easier.

Rio said that since January 2020 it had received one reported case of sexual assault and 29 of sexual harassment that were substantiated, and another report of sexual assault and 14 of sexual harassment that could not be.

Fortescue, Woodside Petroleum and Chevron Corp, also made submissions.

Fortescue said it had 20 harassment matters reported this year, added to 11 last year, across a total workforce of more than 15,000.

(Reporting by Melanie Burton. Editing by Gerry Doyle and John Stonestreet)