Women now account for just over a fifth of directors on boards of top companies after a "culture change" in British business over the past three years, according to a new report.
Former trade minister Lord Davies of Abersoch headed a review in 2011 when the number of female board members in FTSE 100 firms was just 12.5%.
He set a target of 25% by 2015, and reported today that the figure stands at 20.7%, showing "real progress", with more women than ever before in boardrooms of leading companies.
A separate report by the Cranfield School of Management confirmed the trend and revealed that just two FTSE 100 companies - Glencore Xstrata and Antofagasta - had all-male boards, compared to one in five in 2011.
Of the 1,117 FTSE 100 board positions, 231 are women, while 48 new female appointments need to be made to reach the 25% target.
Lord Davies said: "The rate of change that we have seen at the heart of our biggest companies over the last three years has been impressive.
"The voluntary approach is working and companies have got the message that better balanced boards bring real business benefits. We are finally seeing a culture change taking place at the heart of British business.
"However, the eyes of the world are on us as we enter the home straight. They are judging us as to whether the voluntary approach, rather than regulation, will work - we need to now prove we can do this on our own."
Business Secretary Vince Cable said: "These latest figures show that businesses are getting the right mix of talent around their boardroom table and understand the importance of this. Ninety-eight of the FTSE 100 boards are now made up of at least one woman and we need fewer than 50 new women appointments to FTSE 100 boards to reach our target of 25% of women on all FTSE 100 boards in the next year. This is a huge improvement from where we started just three years ago.
"More needs to done to improve the number of women in executive positions. These will be the CEOs of tomorrow and businesses still aren't tapping into the vast talent pool available to them."
Minister for women and equalities Maria Miller said: "It makes clear economic sense for women to be able to rise to the top. Good progress is being made in Britain through a cultural shift that promotes on merit, not through the mandatory quotas advocated by others.
"The workplace was designed by men for men. Women don't need special treatment they just need a modernised workplace that gives them a level playing field."
Professor Susan Vinnicombe, director of the Cranfield International Centre for Women Leaders, said: "Whilst it is extremely encouraging to see the overall figures moving in the right direction, and the 25% target in sight, the issue still remains that women are not being appointed to executive positions, despite there being a wealth of suitable candidates.
"We currently have the highest number of non executive director positions (NED) ever at 826 and the lowest number of executive director (ED) positions ever at 291. These figures show that the likelihood of women being appointed to ED positions is decreasing. Therefore, while it is important to meet the 25% target; we need sustainable change that will ensure diversity on our boards in executive positions as well as NED roles."
Katja Hall, chief policy director at the Confederation of British Industry, said: "These latest figures show the voluntary approach recommended by business to Lord Davies is working. However there is still some way to go, so now is not the time to take our foot off the accelerator."
TUC general secretary Frances O'Grady said: "British boardrooms are moving in the right direction and it's good to see a fifth of senior executive positions are now held by women. But while progress is undoubtedly being made, the pace of change is too slow - and there are still companies with no female directors on their boards. At this rate it'll be decades before we see a 50/50 gender split at the top of British business."
Daisy Sands, head of policy at the Fawcett Society, said: "It's encouraging to see more women reaching the top tables of business. Evidence shows that more women in senior management and boardrooms leads to better corporate performance, a boost to the bottom line, and allows businesses to tap into new insights about their customers."
Lisa Buckingham, of the Institute of Directors, said: "It is encouraging to see how companies have improved boardroom diversity since Lord Davies' initial recommendations in 2011 - particularly as this has been achieved voluntarily without the need for quotas.
"However most of the increase in female representation has been non-executive and the IoD believes strongly that we should be looking for better balanced boards at the executive level."
Cranfield named Capita and Diageo as joint leaders of this year's rankings, each with more than 44% female representation on their boards.
Gloria De Piero, shadow minister for women and equalities, said: "We're making decent progress towards the 25% target, but what is disappointing is that so far it's all coming from non-executive appointments, and when women represent 50% of the population it's a bit early to be celebrating.
"All the evidence shows that lack of diversity is not simply bad for equality, it also leads to poorer decision-making and company performance. That's why, if sufficient progress isn't made to increase the representation of women and ethnic minorities on boards, we will consider introducing more prescriptive measures, such as quotas."
An Equality and Human Rights Commission spokesman said: " The commission welcomes the progress companies are voluntarily making in increasing female representation at board level.
"The commission is concerned, that despite the sector's engagement with Lord Davies, there remains a lack of transparency about appointments at board level. With 48 FTSE 250 boards still entirely male, some companies appear to be falling short of the standards needed for sustainable change.
"That is why the commission is putting in place an in-depth project to investigate recruitment practices at board level."