Women are being held back from company boardrooms by "old boys networks", according to a report by the equalities watchdog.
The Equality and Human Rights Commission (EHRC) found that nearly a third of the UK's biggest companies rely on personal networks of existing board members to find new members. Most board roles are not advertised, the report said.
Looking at the FTSE 100 and FTSE 250, the EHRC said more than 60% have not yet met the voluntary target of 25% female board members.
"Our top boards still remain blatantly male and white," said EHRC commissioner Laura Carstensen.
In 2012-13 and 2013-14, when the study was conducted, less than half of the 350 listed firms increased female representation on their boards. In fact, for executive roles, nearly three quarters of FTSE 100 and nearly 90% of FTSE 250 firms had no women on their boards at all.
Last year, Lords Davies', who implemented the voluntary targets for women on boards, said there were now no FTSE 100 companies will all-male boards. However, the EHRC said the "headline progress" was "masking the reality".
Ms Carstensen said: "The good work of a forward thinking minority masks that many top businesses are still only paying lip service to improving the representation of women on boards.
"The recruitment process to the boards of Britain's top companies remains shadowy and opaque and is acting as a barrier to unleashing female talent."