The so-called glass ceiling that prevents women progressing in the workplace is more like "reinforced concrete", the chief executive of the Equality and Human Rights Commission (EHRC) has warned.
The commission's annual Sex and Power report, which looks at women in positions of power and influence across the public and private sectors, suggests progress has stalled, with only a few significant advances.
The number of females in top roles has dropped in 12 out of 25 categories, with fewer MPs, cabinet members, senior police officers and judges now than 12 months ago. In another five categories, the number of women remains unchanged since 2007's report.
EHRC chief executive Nicola Brewer said: "Workplaces forged in an era of 'stay at home mums' and 'breadwinner dads' are putting too many barriers in the way [of women], resulting in an avoidable loss of talent at the top.
"We always speak of a glass ceiling," she said, "but these figures reveal that in some cases it appears to be made of reinforced concrete. We need radical change to support those who are doing great work and help those who want to work better and release talent."
This report also estimates the number of years at the present rate of progress it will take for women to achieve equality in key areas.
The EHRC report likened women's progress to a snail's pace, for example, a snail could crawl from Land's End to John O'Groats and halfway back again in the 73 years it would take for equal numbers of women to become directors of FTSE 100 companies.
If women were to achieve equal representation among the 31,000 top positions of power the commission has identified, the report claims nearly 5,700 'missing' women would rise through the ranks.