"The home straight is in sight" for top UK firms appointing 25% of women to their boards by 2015, according to the head of the Davies Review steering group.
Denise Wilson, the chief executive of the group set up in 2011 by the government to monitor progress of meeting Lord Davies's 25% target for FTSE 100 firms, said the argument for having more women on British boards was clearer then it was when the group was established more than three years ago.
"Along with Australia, we are two countries in the world that has made really great progress – we just need to keep it up. The home straight is in sight," Wilson said.
But Wilson said the group was "slightly concerned" at the pace of appointment of female executives, which had slowed over the past six months.
"Why are we trailing? I don't know. It might be that we have been over-positive in our messaging," Wilson said.
Wilson, who made the comments at a 30% Club Evolution of the Board summit, said board chairmen have been a "major part" of the initiative's success.
"They have been key to moving the dial. But actually nothing matters more than taking action. It's good to have loyalty and support, but nothing is going to bring progress like a determined, decisive chairman."
Wilson explained that the group have positioned the call for more women on boards as a business issue and not a diversity issue.
"Building the executive pipeline further down is a longer-term task," Wilson said.
"However, we are seeing many, many chairmen and chief executives turning their attention seriously to that.
"We would like to see more women sitting on nomination committees and women who are on boards championing other women in the workplace and opening up opportunities."
The number of women directors on FTSE 100 boards has jumped from 15% in 2011 to 22.8% in September 2014, according to the Professional Boards Forum BoardWatch.
But data from the Department for Business found that 61 of the FTSE 100 firms still have to reach 25%.
"Although our target is in sight, we must keep up the momentum," said Vince Cable, the business secretary.
"All companies with fewer than 25% of women on their board need to take firm action now to increase female representation."