By Alix Culbertson, political reporter
The number of female MPs could plummet for the first time in more than a century if action is not taken now, campaigners have warned.
If Reform UK, which has led voting intention polls since April, or the Conservatives, win the next general election, women's representation would fall drastically.
A Labour win would stall the current percentage of female MPs, which stands at its highest ever at 41% (264 out of 650) - but is still lower than the UK population, of which 51% are women.
If Reform win the next election, set for 2029, women's representation could fall to 26%, analysis of Electoral Calculus polling data by 50:50 Parliament found.
If the Tories win, 33% of MPs would be women, while Labour would remain the same.
50:50 Parliament, which campaigns for gender equality in politics, is calling for people to "Ask Her to Stand" to encourage more women to get involved with politics to help balance the scales.
It has installed a "push for equality" panic button outside parliament to raise awareness of the gender disparity.
What does history tell us?
Every parliament since women were allowed to be MPs in 1918 has seen an increase, apart from small drops in 1950, 1979 and 2001.
Nancy Astor was the first woman to take her seat in the Commons and served from 1919 to 1945.
The 80s saw a substantial increase in female MPs before a large jump in 1997, and there has been a big rise from 128 women MPs in 2005 to the current 264.