Businesses will have to act faster to improve the number of women on boards or face the possibility of quotas being imposed, a leading pressure group claimed on Thursday.

Prime minister David Cameron told a conference of Baltic-Nordic leaders that he was against imposing quotas on businesses, but said that he would not rule this out. Currently, 15 percent of directors on FTSE 100 boards are female, but Cameron said he wanted to raise this to 30 percent.

Helen Morrissey, who is a founder of the 30% Club, which lobbies for more women on boards, said: "Quotas are still a threat not a reality, and British businesses need to act faster if they want to improve the diversity of their boards voluntarily rather than have change imposed on them."

The CBI business group said firms were making "good progress" on getting more women on boards but added there was "clearly much more to be done".

"Last year, over 100 women were appointed to FTSE 350 boards, and a new voluntary code was introduced for head-hunters," it said in a statement. "Real momentum is building on this issue, and this year a change to the Corporate Governance Code will require firms to examine and report on steps they are taking to improve diversity within their own organisations."