Burberry’s Angela Ahrendts is one of just three women to head FTSE 100 Index companies along with easyJet’s Carolyn McCall and Alison Cooper at Imperial Tobacco.
That number could be temporarily boosted later this year with the increasing likelihood that Royal Mail – headed by chief executive Moya Greene – will join the top tier in the December reshuffle, after its storming stock market debut.
Ms Ahrendts will leave Burberry by the middle of next year, to be replaced by the luxury handbag group’s creative boss Christopher Bailey.
The number of top tier female bosses has been eroded by the departure of Marjorie Scardino from Financial Times publisher Pearson and Cynthia Carroll from Anglo American in recent months, offset by easyJet’s promotion to the FTSE 100 in March.
Ms Carroll left mining giant Anglo American in April, while Dame Marjorie quit the publisher of the Financial Times at the end of last year.
The Government is attempting to tackle the gender imbalance on company boards, and recently hailed progress in hitting a target of 25% by 2015.
Figures from the start of the month showed 19% of directors of FTSE 100 companies were women, up from 12.5% three years earlier.
But while the number of female non-executive directors on FTSE 100 company boards had risen to 23.8% from 15.6%, the number of female executive directors had edged up to just 6.1% from 5.5%.
Among FTSE 250 Index companies, 14.9% of directors were women, up from 7.8% in 2010. But of these, 18.6% were non-executives and just 5.4% were executive directors.
Notable chief executives among second tier firms include Ruby McGregor-Smith, chief executive of outsourcing group Mitie, Dorothy Thompson, boss of power station Drax, and Harriet Green, who heads tour operator Thomas Cook.
Lord Davies, who chaired the Government’s original Women on Boards report in 2011, said the industry has come a “long way” since then.
He said: “We have now moved to a place where it is unacceptable for the voice of women to be absent from the boardroom.”
Rowena Ironside, chief executive of action group Women on Boards, said: “The pipeline of women qualified for board roles is weaker in many sectors than the pipeline of men.”