More than half of the country's ASX200 listed companies don't have a female board director - prompting one gender advocacy group to release a name-and-shame report on the gender imbalance that continues to prevail in the financial services sector.

Women on Boards (WOB) has long campaigned for better representation of women in high-ranking roles, particularly in executive boards. While women in Australia already make up 63 per cent of university graduates, only a fraction ever makes it to a CEO role.

This week WOB ramps up its lobbying through a new index, called the Boardroom Diversity Index, which will track the ratio of men and women on the boards of listed companies, super funds and credit unions.

Two months ago, the group made a submission to the government asking for changes to the ASX Corporate Governance rules, including a policy to factor gender diversity in director recruitment guidelines.

The renewed campaign follows WOB research that reveals how poorly represented women still are on executive boards.

According to the inaugural research from the Boardroom Diversity Index, the number of women on boards went up a tiny 0.4 per cent to 8.7 per cent this year compared to last year.

The number of companies without a female director still sits at a high 53 per cent - despite Women on Board's database of more than 7,000 professional women seeking directorships.

The group said that if things don't improve in the next few years, it will lobby for a ‘mandatory quota' of women on listed companies, or to set gender targets.

"We prefer companies to achieve gender equity through voluntary targets, but there comes a time when enough is enough - and Australia's professional women have just about reached that point," said Ruth Medd, chair of WOB.

She said more could be done on how boards select directors.

"A key reform is removing the major barriers to women achieving directorship roles - the lack of transparency in the current system of board appointments and an unwillingness to broaden the search beyond the narrow pool from which directors are chosen," she said.