Proposed changes to the UK Corporate Governance Code will, from 1 October 2012, require companies to publish their policy on diversity in the boardroom as efforts to reduce the gender imbalances at the hierarchy of FTSE businesses increase.

From next month, all companies with a Premium Listing of equity shares in the UK will be expected to make public their plans to increase boardroom diversity and report against it on annual basis.

Chris Hodge, director of corporate governance FRC, said: 'From next month boards will need to have a diversity policy, this isn't just about gender diversity but it will be left to the companies as to what that policy looks like.

'We are seeing particularly in the top 100, a realisation that diversity is good for the board as an all-white, male team is more prone to group think.

'They [the FTSE 100] do have a greater awareness of the need for diversity but, having larger boards, are also able to get a wider range of backgrounds more easily.'

The measure is just one of the recommendations made by Lord Davies in his Women on Boards report, published in February last year, which also suggested that women should make up 25% of FTSE boards by 2015.

In April, a study by Cranfield revealed that nine FTSE 100 companies did not have a woman on their board and that the number of female-held directorships across the top 100 had risen to 16%.