Mothers of young children are losing out on over a billion pounds in earnings each year, according to a charity.
Save the Children warned that mothers are missing out on millions daily due to "a childcare system that feels stacked against them".
The charity used available government figures to look at the employment patterns of women with children aged under five.
It calculated that there are around 450,000 women in this category in England who would like to work, or work more, and of these around a fifth say that childcare is the key factor preventing them from working.
The charity used this figure, and data on mothers in work with different levels of qualifications, to estimate how much women who would like to work, or work more, are losing out.
It concludes that nationally, they are losing out on £1.2 billion every year.
Steven McIntosh, Save the Children's director of UK poverty policy, advocacy and campaigns said: "Mothers describe a childcare system that feels stacked against them. They tell us it's nightmare to navigate with barriers to work at every turn.
"The result is an astounding loss in earnings, hitting families already battling to make ends meet. The financial pressure and stress that creates at home is never good for parents or their children. It's time to make childcare work for families."
A Department for Education spokesman said: "We have doubled the free childcare available to working parents of three and four year olds to 30 hours a week, saving parents up to £5,000 a year per child, and over 200,000 children have already benefited from a 30 hours place since September.
"Our independent evaluation of the early rollout of 30 hours free childcare showed that nearly a quarter of mothers and one in 10 fathers increased their working hours as a result.
"We are tackling the barriers for parents to return to work by introducing shared parental leave, new rights to request flexible working and our £5 million returner programmes that will make it easier for people to get on with their careers after taking time out for caring."