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The number of all-male FTSE 100 boards has fallen to single figures for the first time in history, thanks to the drive to encourage more women on boards, the latest data showed on Monday.

The number of women currently sitting on the boards of the UK's top companies rose to 16 percent, from 15.6 percent in March, with all male-boards falling from 11 to nine, according to the latest data from the Cranfield Female FTSE report.

A total of 153 women now hold 176 board positions at FTSE 100 companies out of the 1,098 board positions available. In March 141 women held 163 FTSE 100 board seats.

"It is really encouraging to see a continuing fall in the number of all-male boards and so soon after publishing last month's report," Dr Ruth Sealy, deputy director of the Cranfield International Centre for Women Leaders, said in a statement.

As at 19 April the FTSE 100 companies with all-male boards included Amec, Antofagasta, Croda, Glencore International, Intertek Group, Kazakhmys, Randgold Resources, Vedanta Resources and Xstrata.

Dr Ruth said however that she was "aware of one or two" of the nine remaining all-male FTSE 100 boards that are looking to appoint their first female director.

In February 2011 Lord Davies published a government-sponsored report that found only 12.5 percent of boards at the UK's leading companies included female directors. 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 Jackie Hunt, CFO of insurer Standard Life, to recently tell CFO World that: "I worry that we'll win the battle and frankly lose the war."

The UK's public companies will have to report annually from 1 October on their boardroom diversity policy.