Nick Clegg has vowed to try and slash "nightmare" childcare costs for parents who go back to work.
The Deputy Prime Minister condemned as "absurd" the fact that many mothers were forced to stay at home because the "sums don't add up".
The comments, in an email to around 100,000 Lib Dem activists, suggest the party will be lobbying the Chancellor to increase subsidies for nursery places in next month's Autumn statement.
One option could be increasing the 15 hours per week of state-funded childcare currently available to three and four-year-olds to 25 hours.
Mr Clegg wrote: "An issue that gets raised again and again when I speak to people across the country is the question of good childcare - and how important it is not just to families but to our economy, too.
"When it comes to finding a nursery, a childminder or a nanny, it can be a real nightmare.
"For too many parents that's first and foremost because of cost. I know so many mothers who've been really keen to get back to work after their year of maternity leave - until they've calculated the cost of a place at nursery.
"Add in the cost of travel to work and mums can find themselves effectively working full time for just a couple of pounds a week. It's absurd."
The Lib Dem leader continued: "Even mothers who do go back to work after their first child can find it impossible when it comes to the second child.
"Too often they just can't make the sums add up, and even though they'd love to be out earning they find years go by before it makes financial sense.
"So, by the time they can afford to go back to work, it's a struggle to find a job and convince an employer they've still got what it takes."
Mr Clegg highlighted last week's report by the Resolution Foundation which warned the only way to raise living standards for people on low and middle incomes was supporting women to work.
Lib Dems have praised the think-tank's suggestion of providing an extra 10 hours a week of childcare at a nominal rate of £1 an hour for three and four-year-olds.
"Of course there's no silver bullet," Mr Clegg said. "Everyone knows there isn't much money to go around and looking after small children is a difficult job which should be done by skilled people who know what they're doing. Childcare isn't something you can buy at bargain basement prices.
"But I'm determined to make sure we do more, and do it better. I've got a simple objective in mind: I want every parent who wants to work to be able to - without seeing every penny of their wages disappear in childcare bills.
"If we can find the money, we'll try to make that possible."