In February 2011 Lord Davies published a government-sponsored report that found . Lord Davies issued chairmen with an ultimate -- ensuring a minimum target of 25 percent of female representation on FTSE 100 boards by 2015 or face a strict quota.

"We have always been clear about the untapped female talent pools and I am delighted with the progress that has been made, particularly in recent months," said professor Susan Vinnicombe, co-author of the report.

The report said some companies are going above and beyond the level set out by Lord Davies. National Grid has announced its fourth female board member, Nora Mead Brownell, will take up a non executive position from 1 June, taking the company into the "illustrious ranks" of those companies with over 30 percent female representation.

Cranfield now predicts 26.7 percent of directors could be women by 2015 and 36.9 percent by 2020, which will exceed the targets set in the Davies report.

Despite progress concern however remains that the majority of female appointments to board are for non-executive positions rather than executive positions, leading , to recently tell CFO World that: "I worry that we'll win the battle and frankly lose the war."