Despite a 10% overall increase in non-executive directors, there has been minimal increase in the diversity of the board in big UK companies, according to Carol Arrowsmith, Deloitte head of remuneration.

She said the lack of women non-executive directors was a lack of concern. The latest Deloitte board structure research found only a slight increase in the number of female FTSE 350 executive board members - up from 3% to 4% - but no increase in the number of female non-executives.

The research also found many FTSE 350 boardrooms are failing to achieve the recommended 50:50 ratio of executive to non-executive directors. Independent directors are making up less than a half of boards at 29% of FTSE 250 companies and 11% of FTSE 100 firms.

The increased responsibilities of non-executive directors have had a significant effect on fee levels which continue to rise at a higher rate than before for these positions and are currently slightly higher than increases in executive salaries. Total fees in the past year grew by 7.3% compared to 7.1% last year.

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Grappling with diversity

Female board members up 40%