More larger companies are hiring female directors, helping to boost their numbers by 240,000 over five years, a study has found.
The overall number of company directors has increased since 2007, according to information services company Experian, with more of them women than men.
The study of over 2.7 million businesses found the number of female board members was up by 24%, compared to 15% for their male counterparts.
Small companies, with between three and 10 employees, remain more likely than firms with over 250 workers to have female directors - but the gap is narrowing, Experian found.
In 2007, just 33% of larger companies had at least one female director, while in 2012 it had risen to 40%.
The number of smaller firms with at least one female executive was up from 48% in 2007 to 50% this year.
The report also found that a third of the 1.4 million businesses started since 2007 had one or more female director.
Experian's UK Managing Director said the research showed a more in-depth picture of women in the workplace across the UK than looking just at FTSE 100 companies.
"Smaller companies are clearly the driving force for female directors, but our research shows that larger companies' efforts to increase the number of female directors has made a significant difference over the past five years," Max Firth said.
"And let's not forget the contribution made by female entrepreneurs, with many starting up their own companies to manage work/life balance and fit with family commitments, without whom the number of female directors would be considerably lower."
But although the figures appear to show a step in the direction of workplace equality, Experian found little change in the industries dominated by females over the last five years.
In 2007, hairdressing, primary education and social work were the professions with the largest percentage of all female boards and this trend has increased further.
And in typically male-dominated professions, like plumbing, installation of electricity and software publishing, there were fewer all-female boards in 2012.
Mr Firth described the picture as "fairly static" when different industry sectors were compared.
"Whilst there are undoubtedly many women who are breaking new ground and overcoming stereotypes, our data shows that amongst the total population of UK companies, the industries with most female directors are pretty much the same as before the recession," he added.