An academic study led by Edinburgh University, found women have "at best, a 20% chance of being made non-executive directors". It found those hired are paid 8% less than male counterparts.
The experts found no pay gap or hiring bias at executive level, but put this down to " public scrutiny".
The study analysed British firms on the FTSE-350 between 1996 and 2010. The percentage of female directors rose from more than 2% in 1996 to more than 8% in 2010. However, the chances of women being appointed to boards remain low. Report author Professor Brian Main, of the University of Edinburgh, said: "They are not thinking aggressively enough or openly enough about appointing women to all positions."