Some two-thirds of Britain's top 100 companies have so far ignored calls to set targets for boosting the number of women they have on their boards, a progress report revealed today.
The Government-commissioned Lord Davies review, published in February, recommended that firms listed on the FTSE 100 Index should aim for a minimum of one in four female board members by 2015.
But an official progress check by the Cranfield School of Management found just 33 companies have heeded this recommendation.
Elsewhere, the Cranfield report said 21 women have been appointed to board positions out of a possible 93 - representing 22.5% of all new appointments, short of the 33% recommended by former trade minister Lord Davies of Abersoch.
In February, Lord Davies called on chairmen to announce their targets for 2013 and 2015 within six months, but only 33 have heeded this recommendation.
The Cranfield report said Lloyds Banking Group and Rolls-Royce stood out for "boldly" aiming to increase their female representation by between 20% and 23%.
There was some progress since the review was published, the Cranfield report said, with the number of women holding FTSE 100 board directorships increasing from 12.5% to 14.2%, or 155 out of a total of 1,092 positions.
Ruth Sealy, co-author of the Cranfield report, said: "The results from our report suggest the recommendations in Lord Davies's review have had beneficial effects in terms of reinforcing good practice, but they also demonstrate an institutional inertia, whereby companies persist in their existing approach - or lack thereof - to gender diversity on boards.
"It is so important that our top companies set the standard for achieving better representation on their boards."
Elsewhere, the FTSE 250 Index has seen 28, or 18%, out of a possible 158 new appointments go to women.
Commenting on the update, Lord Davies said: "This is about good business practice, it is also about securing performance.
"You need engagement and diversity in teams to achieve success. Too many UK boards and executive teams do not have it. We are working to change that."
The results of the Cranfield report will be discussed later today at a Downing Street event with Prime Minister David Cameron to celebrate women's contribution to UK business.
Mr Cameron is understood to be writing to companies that have yet to draw up targets for increasing female representation to encourage some action.
Helen Wells, director of gender campaign Opportunity Now, said: "The move towards setting aspirational goals for the number of women on corporate boards is gathering pace.
"Those FTSE 100 and FTSE 250 companies who have not yet published their goals should do so, or risk being left behind in the race for talent."