More than one quarter of Australia’s top 300 companies have no women on their boards, while the number of females directors at some government-owned corporations has gone backwards.

A study commissioned by lobby group Women on Boards has found 81 of the companies that make up the ASX 300 have no female directors, despite improvements in gender equality among the top 50 and 100 companies.

Just under a quarter of directors with ASX 100 companies are women, which is a five per cent improvement compared to 2013, the Boardroom Diversity Index showed.

Only five companies in the top 100 had no female directors: TPG Telecom, Ramsay Healthcare, Qube Holdings, Sirtex Medical and Domino’s Pizza Enterprises.

But gender equality at government-owned corporations has gone backwards federally, and in Queensland and Western Australia since 2013.

“It is clear to us that the message is starting to hit home in a number of important areas in the economy – in particular superannuation and ASX companies – but unfortunately not with some governments,” Women on Boards director Claire Braund said.

Braund also drew attention to the fact that conservative governments had overseen the slide in female board representation in each jurisdiction, though Queensland had elected a Labor government in early 2015.

“It’s hard not to conclude that conservative leaning governments are bad for women,” she said.

The number of women on boards at federal government-owned corporations fell 0.8 per cent during the past two years to 38.5 per cent, which compares to a 13.5 per cent fall in Queensland and 3.2 per cent slide in Western Australia.

But there was a 7.2 per cent increase in women on the boards at government corporations in NSW, which also has a Liberal government.

– AAP