Statistics released by the Department for Business Innovation and Skills (BIS) showed that women account for 22.8 percent of directors at companies in the FTSE 100 blue-chip stock index <.FTSE>, up from 12.5 percent three years earlier.

However, the report also said women made up less than the minimum target of 25 percent of the boards at 61 percent of businesses in the index, in a country where women have had the vote for a century and serve in the armed forces.

The government figures show Britain lagging countries such as Norway, which in 2003 pioneered gender quotas, requiring nearly 500 firms to raise the proportion of women on their boards to 40 percent.

If companies don't seek out more women board members, "I think there is a threat that quotas will be brought in ... by the European Union," said Fiona Hathorn, managing director of Women on Boards UK.

In 2011, a UK government review chaired by former Trade Minister Lord Mervyn Davies recommended that all companies in the index of leading London-listed shares should aim for women to make up at least a quarter of their boards by 2015.

"Although our target is in sight, we must keep up the momentum. All companies with fewer than 25 percent of women on their board need to take firm action now to increase female representation," Business Secretary Vince Cable said in a statement.

Together with Davies, Cable also wrote a letter to the 29 companies in the mid-cap FTSE 250 index with all-male boards, urging the firms, which include retailer JD Sports (>> JD Sports Fashion PLC), to appoint at least one female director "in the short term".

No FTSE 100 company has an all-male board since miner Glencore (>> Glencore PLC) appointed Patrice Merrin as its first female board director in June after shareholder pressure.

(Reporting by Liisa Tuhkanen; Editing by Ruth Pitchford)

By Liisa Tuhkanen

Stocks treated in this article : Glencore PLC, JD Sports Fashion PLC