The number of British women in senior roles has fallen by almost 40 per cent in the past five years as they either abandon the struggle to juggle family and career or quit to start up their own businesses.
What's more, research by PricewaterhouseCoopers has found that women are turning their backs on corporate life at an increasing rate, with the number of women in senior posts in FTSE 350 companies having fallen to 22 per cent this year, down from 38 per cent in 2002.
Meanwhile, while some progress is being made at the most senior levels, where the number of FTSE 350 female full-time chairmen or chief executives has grown, their numbers can still be "counted on one hand", the PwC report said.
But while the findings will inevitably cast doubt on the effectiveness of efforts by organisations to increase the number of women in senior positions through initiatives such as flexible working arrangements and formal diversity policies, they also suggest that many talented women simply prefer to start their own businesses rather than remain shackled to conventional organisations.
Nevertheless, the survey also identified childcare issues as a factor in the decline in women at senor levels, suggesting that many opt out of the workforce at an earlier stage of their careers because they simply cannot afford its extortionate cost.
The cost of a typical full-time nursery place in England has increased by more than a quarter in the past five years according to the charity the Daycare Trust, far out-stripping inflation.
Average fees in England for a full-time nursery place for a child under two are £152 ($275), rising to £205 ($375) in central London.
Yet women in senior executive roles are likely to have a larger disposable income, meaning they are better able to meet the considerable financial commitments of flexible childcare needed to follow a high-flying career and raise a family at the same time, said PwC.
The other major factor contributing towards the gender exodus overall appears to be a rapid increase in the numbers of women setting up in business for themselves.
The number of self-employed females in the UK has now risen above a million for the first time, according to the Labour Force Survey while figures from the Department for Trade and Industry suggest that the number of businesses wholly or predominantly owned by women has risen to 17 per cent.
Sarah Churchman, head of diversity at PricewaterhouseCoopers LLP, said: "At the top, things are moving slowly in the right direction but our middle management data paints a very different picture.
"Businesses tend to pay more attention to gender issues in senior positions and there appears to be an assumption that a supply from the middle ranks will eventually feed through. For big companies at least, this pipeline is shrinking at a worrying rate," she added.
"There has been progress on equal pay but it can be difficult to tackle the cultural and external financial issues that drive peoples' behaviour and life-choices," Churchman continued.
"Smart companies will monitor work force trends in this, and other, areas. It makes business sense to ensure talented people have opportunities to continue their careers as their circumstances and needs change throughout their working lives," she concluded.
The departure of senior manager females was mirrored for "heads of function", the next level up, the survey also found.
The FTSE 250 had a similar proportion of women stepping off the corporate ladder (43 per cent) as the FTSE 350.
But Britain's top companies were managing to attract and retain women at this level – more than a tenth of "head of function" positions in the FTSE 100 were held by women in 2002, and this had increased to a fifth today, it found.
The findings also showed which UK locations had the highest proportion of women in senior roles – central London, London as a whole, Glasgow, Bradford, Manchester, Edinburgh and Bristol.