Britain's top companies have made "enormous progress" on gender diversity by doubling the number of female directors, new figures indicate.
Lord Davies, the former trade minister, said women now accounted for 23.5% of FTSE 100 board members, up from 12.5% in 2011.
The increase means that companies are on track to meet his 25% target for 2015.
"The voluntary approach is working - boards are getting fixed," he said.
The government report found that there were now 263 female directors in FTSE 100 companies, meaning a further 17 women need to be appointed this year to meet the 25% target.
Risk of stagnation
However, the latest statistics showed that smaller companies were less diverse at the top, with women accounting for just 18% of directors on the boards of FTSE 250 firms - although that was a sharp rise from 7.8% in 2011.
"This is a journey of small steps," Denise Wilson from the Lord Davies Women on Board Steering Group told Radio 4's Today programme.
The latest figures show great progress, she said, but agreed that getting women into executive director roles at Britain's biggest companies still posed a challenge.
"We always recognised this was going to be the toughest nut to crack," she said.
An annual benchmarking report by the Cranfield University School of Management, published alongside the government report, said 41 firms in the FTSE 100 and 65 in the FTSE 250 had now met the 25% target.
Drinks firm Diageo and Intercontinental Hotels Group jointly topped the Cranfield ranking, with 45% female representation on their boards.
But Dr Elena Doldor, co-author of the report, said she expected women's representation on boards to stagnate at about 28%.
"There are still not enough women on executive committees or in the executive pipeline. Introducing aspirational and measurable targets for women at all levels is the only way to achieve real progress," she added.
Women's progress at the top:
- FTSE 100 companies have 263 female board members - 23.5% of the total
- FTSE 250 companies have 365 female board members - 18% of the total
- There are no all-male boards in the FTSE 100
- There remain 23 all-male boards in the FTSE 250
'Still work to do'
The Cranfield report also compared the UK's progress to the rest of the world over the past decade, saying Britain's progress meant it ranked fifth globally.
CBI deputy-director general Katja Hall said the statistics showed the voluntary approach to increasing diversity in business was working.
"To keep up momentum businesses must now continue to work on building the talent pipeline by supporting more women to take on management roles and helping mothers return to work," she added.
Similarly, Lisa Buckingham, senior adviser on diversity at the Institute of Directors, said more needed to be done.
"Company boards, senior executives, employees, the wider public, appointment committees and recruiters, especially, all have a role to play. They have made an impressive start but there is still work to do."