The share of female professors has edged up slightly, but they are still out-numbered more than five to one by their male counterparts, figures show.
More women work part time
Some 17.5% of professors in the UK were women in 2006-7 - up from 16.7% the year before, the Higher Education Statistics Agency shows.
And 36.8% of senior lecturers and researchers were women.
The Universities and College Union said there was no reason why more women should not be in top university jobs.
UCU general secretary Sally Hunt said: "Fair, open and transparent recruitment and promotion procedures are in everyone's interests, not just women.
"What is equally important for the future is that institutions act to ensure equality of opportunity at every point so that women who are at the start of their academic career will face fewer obstacles in getting to the top."
The figures also showed the proportion of academic staff in all grades increased from 31.9% to 42.3% over the same period.
Many more women than men are still working part time - 41.8% of female academics compared to 26.8% of male academics.
And nearly two-thirds (or 62.6%) of non-academic staff were female.
A spokesman for university umbrella group Universities UK said: "We are pleased to see the increase in female academics for 2005/06. We are particularly pleased to see the increase at professorial level.
"However, we are not complacent and recognise there is always more that can be done."