The gender pay gap has widened in WA, where women earn on average $43,000 a year less than men.

West Australian women continue to be diddled by their employers, with full-time workers earning on average 30.9 per cent - or a whopping $43,000 a year - less than men.

That compares to the national average gender pay gap in 2015-16 of 23.1 per cent or nearly $27,000.

New data released by the Workplace Gender Equality Agency on Wednesday showed WA's gender pay gap had bucked the national downward trend, rising from $41,500 or 30.5 per cent in 2014-15.

The figures showed the state also had the lowest representation of women at all levels of management.

For those females in management in WA, however, the gender pay gap was narrower than the Australian average last financial year.

Chief executives, for example, earnt 12.6 per cent less than their male counterparts compared to 16.3 per cent nationally.

West Australian women in financial and insurance services are particularly hard done by, earning 33.5 per cent less than men in the same profession.

The WA opposition's Simone McGurk noted Premier Colin Barnett's plan to slash penalty rates for Sunday and public holiday shifts, also revealed on Wednesday, would mainly affect female-dominated industries such as hospitality.