The Maritime Union of Australia is threatening to pursue WA's biggest marine services provider over an incident in which "sexist and derogatory" remarks were allegedly made about a female employee over a two-way radio.
Union officials claim up to 50 other workers heard the offensive comments, about female genitalia, that were allegedly made about the woman in December when she was working at Mermaid Marine's Dampier supply base.
Mermaid Marine Australia's managing director Jeff Weber denies the incident happened, saying the company is yet to receive a formal complaint about it despite an investigation.
MUA WA secretary Christy Cain said the woman's female co-worker had complained to the union after she repeatedly raised the issue with her supervisors and it was not resolved.
Mr Cain said the union had since approached Mermaid Marine several times on behalf of the female employee.
He said they would take Mermaid Marine to the Equal Opportunity Commission if the company continued its refusal to act on the woman's allegations of sexism in the workplace.
"When the woman complained to her supervisor about being subjected to these belittling comments, she was told that since she was working on a wharf, she should expect this type of language," Mr Cain said.
"In this day and age, it's simply not on for women to cop this type of language in the workplace.
"A number of the woman's female colleagues who heard this exchange over the two-way were offended by the language used and they are even more offended that the company is refusing to take the complaint seriously."
Mr Weber said the union's claims were unsubstantiated, with an investigation into the alleged incident failing to find any evidence of it occurring.
He said the company had "zero tolerance" for the kind of behaviour described by the MUA but no complaint had been made that could be followed up.