A 25% target should be set for women senior executives in the country's biggest companies, according to a business leader.
Carolyn Fairbairn, director-general of the CBI, said there are just nine more female executive directors on boards of FTSE 350 companies than in 2010, while the number of women chief executives has barely moved.
She will say in a speech on Thursday that progress has been made following the Davies Review on women on boards, but fewer than 10% of executive directors in FTSE 100 firms are female.
"We don't have enough women running things and it is not getting better anything like fast enough.
"There's no doubt in my mind that developing more women leaders will make a real difference to the success of the UK economy, our productivity and the UK's future place in the world.
"Diverse voices - people of different genders, from different parts of the world, and of different lifestyles, ages, sexuality, religion, physical and mental health capabilities - enable better business decisions," she will say.
"More and more chief executive officers are telling me that their best women are choosing to step down just as they get into very senior positions and are being offered top jobs.
"As a result, too many of our firms are seeing an exodus of senior women. We have talked a lot about glass ceilings over the years, but in my view we now need to talk more about sticky floors. Why are women choosing to leave?"
A target of 25% is "deliberately ambitious" but is appropriate, she believes.
A Business Department spokesman said: "We encourage all companies to improve representation of women at all levels in their organisation. Following the Lord Davies review there are now no all-male boards in the FTSE 100 and only 16 in the FTSE 250.
"The Government is now looking at the talent pipeline of capable women to ensure we build on this momentum. We expect soon to announce a new chair to lead an independent review into improving representation of women in the executive layer of the FTSE 350."