Oil giant Chevron is under fire for medical questionnaires which ask job applicants if they are pregnant, take birth control, have had an STD or an abortion, among other private issues.
The Maritime Union of Australia has complaints from job applicants, including office staff, who claim they are made to reveal deeply personal information that has no bearing on their work.
The questionnaire has compulsory questions such as whether an applicant is pregnant, capable of getting pregnant, takes birth control or female hormones, their menstruation dates and whether they had ever had an emotional problem or an STD.
Optional questions about reproduction ask whether they or their partner has had an abortion, a stillbirth, a sterilisation or had tried unsuccessfully to conceive over a year.
MUA organiser Matthew Elliott said angry applicants felt pressured to finish the optional section to get the job.
Compulsory questions ask about alcohol and cigarettes.
Lawyer Mark Hemery said many questions, especially about pregnancy and contraception, could breach discrimination laws on gender and disability.
Only medical questions related to a person's ability to perform the role being sought were legal.
Mr Hemery said even the questions relating to reproduction were potentially illegal, despite being optional, because of pressure to comply.
However, he said many of the questions were relevant because they indicated an ability to work long hours, potentially in a hazardous environment far from a major medical facility.
It is understood the same questionnaire is used for all jobs across the US company's global operations.
A Chevron spokeswoman said the information was used solely by medical professionals to assess fitness for work.
She said the company was committed to its employees' health needs, with many mobile or working in remote areas with limited medical care.
Its medical documents were guided by industry standards to ensure staff were safe and fit to work. Medical information was used solely by medical professionals and questions on reproductive history were explicitly voluntary so they were legal.