Senior women in the bureaucracy told researchers from the University of Canberra they had to cope with a ''boys club'', they were seen as ''soft and fragile'' and reported pressure to conform to ''aggressive'' and ''masculine'' working cultures.

The study by the university's ANSZOG Institute for Governance looked for the first time at levels of senior female leadership in six Commonwealth departments and found ''a fundamental disjuncture between the formally espoused values of the APS and its practices''.

The study's final report, Still Not 50/50, will be launched at a conference at Old Parliament House on Thursday, and even warns that, in a time of public service cuts and downsizing, any gains that have been made in the past 20 years are in danger of being eroded.

Fifty-seven per cent of the public service workforce is female but only 39 per cent of its senior executives are women. In some departments, such as defence, the level of female senior leadership is as low as 27 per cent.

Only four out of 20 departments are headed by women and three of those are departments with traditionally strong female representation: education, health, and families and community services.

One of the project's leaders, Emeritus Professor Meredith Edwards, said this was the first time a gender equality research project had been undertaken on such scale in the service and that it exposed a yawning gap between what the federal bureaucracy practised and what it preached.

''There's rhetoric and reality,'' she said.

Professor Edwards, a former deputy secretary of the Department of the Prime Minster and Cabinet, said a key to getting more women into senior jobs was flexible working arrangements, but they were practically non-existent in the service's elite senior executive service.

''We got equal opportunity legislation in 1984 and we got permanent flexible part-time work around that time as well,'' Professor Edwards said.

''But if you look at senior executive service women, less than 5 per cent are in part-time employment. I was flabbergasted when I saw that figure.

''That just shows that the rhetoric is there around flexibility about part-time work but the reality is different and increasingly so in a 24-7 world.

''One of the really big issues, if we're going to change the culture, is how we mainstream flexibility in the workplace both full time and part time.''

Professor Edwards said little had changed since the 1980s.

''I was writing in this space back then, in the mid-1980s,'' she told Fairfax Media.

''There is a paper that [now Public Service Commissioner] Steve Sedgwick gave in 1994 and, if you read that report today, you could tweak it a little and you could be talking about today.

''The figures are different but the cultures are very similar.''

But Mr Sedgwick told Fairfax Media he believed much progress had been made pointing out that women made up just 0.2 per cent of senior public service executives then, compared with 39 per cent today.

The commissioner also said some factors relating to under-representation of women in senior levels were historic and would have less of an effect in the coming years.

''I gave you the data going back through my lived experience, in a sense, in the public service in looking at the way that the numbers of women in senior jobs has risen over time,'' Mr Sedgwick said.

''Now, the journey is not over, we're still not 50-50 but we're in that zone.''