General election 2019: Labour and Lib Dems pledge extra childcare support
Both Labour and the Lib Dems have pledged extra money to support the parents of young children.
Labour vowed to spend £1bn on opening 1,000 new early years centres in England, saying they would get parents back to work and help children achieve.
The Lib Dems are promising working families subsidised care for children from the age of nine months.
Lib Dem education spokesperson Layla Moran said the £14.6bn policy was "an investment in the country's future".
The Conservatives say they are already "investing record amounts in high-quality childcare".
Childcare providers have expressed scepticism at the lack of funding details and warned of an "electoral arms race" on childcare promises.
- Children's centre closures 'as high as 1,000'
- Sure Start 'big benefits' but face closure
- Your 30-hour free childcare questions
On a visit to Leeds with shadow Labour education secretary Angela Rayner, Mr Corbyn will promise to open a new generation of Sure Start centres, which provide health, welfare and education services for pre-school children.
Ms Rayner said she was proud of the policy, since she went to a Sure Start centre when she had her son at the age of 16 that she said taught her to "love and nurture and read to my child".
"My mum couldn't read or write and didn't know that cuddling and giving love to your child is really important," she told BBC Radio 4's Today programme.
"Sure Start really changed the life chances for my children and I'll be forever grateful for that."
Asked whether all parents, regardless of income, should be offered help from Sure Start centres, she said they were about more than a household's financial situation.
"I'm talking about not having the basic understanding of how to nurture a young child and any parent can be put in that situation."
She said the UK could afford to invest more in support for young children.
"We can't afford not to do it because we know that anything we try to do after the early years is playing catch up," she said.
Giving parents more free childcare would help them back to work and support the economy, she added.
According to a report from the Sutton Trust last year, up to 1,000 Sure Start centres have closed in the past decade, with funding pressures being blamed.
Labour says it will "reverse the cuts" in the centres which were originally launched when Tony Blair was prime minister.
An analysis from the Institute of Fiscal Studies earlier this year said Sure Start had made a positive impact, with evidence that the health advice had "significantly reduced" the numbers of children being admitted to hospital.
But the financial think tank said it had been a story of a "fast roll-out followed by deep spending cuts", with spending peaking at £1.8bn in 2010 and then being cut to £600m by 2017-18.
The IFS puts the number of closures at about 500 sites - half the Sutton Trust estimate.
Labour has also restated its commitment to providing 30 hours-a-week of childcare for all two-to-four-year-olds, as part of its overall £4.5bn childcare package.
Mr Corbyn said opening a Sure Start centre in "every community" would "unlock the potential of every child".
He said: "Parents are struggling to afford the childcare support they need, while many children are going hungry and growing up homeless."
Childcare from nine months
The Liberal Democrats are unveiling their own childcare plans - offering 35 hours a week of care for all parents of two-to-four-year-olds.
This would be available for working parents from when their children are nine months old.
The Lib Dems say this will be funded by "fair tax changes", which they say means "making sure that big businesses pay their share".
The party's education spokesperson said investing in childcare was "an investment in the country's future".
"It doesn't just help in terms of high early years provision making school children school ready, but also in closing that gender pay gap, which is incredibly important."
Ms Moran told the Today programme the total cost of the policy was £14.6bn, which was "fully costed" as part of her party's manifesto.
"It's going to be an expensive policy we've been very upfront about that," she said.
"The true cost to child care providers of doing this is more than has been provided."
At present working parents of three- and four-year-olds in England are entitled to 30 hours' free childcare a week - and the Conservatives say they have increased the funding and quality of childcare provision while in government.
Neil Leitch, chief executive of the Early Years Alliance, welcomed Labour's promise for new Sure Start centres.
But he raised concerns about funding the promises - and whether there would be adequate levels of payments for nurseries and childcare providers.
"This is a positive policy for the thousands of parents struggling to afford childcare - but the lack of detail on how it will be funded will strike fear into the hearts of many providers.
"We currently have a funding shortfall in the early years of two-thirds of a billion pounds. That shortfall, which has led to thousands of provider closures, is a direct result of an ongoing electoral arms race between political parties to entice parents with 'free childcare' without thinking through how it will be paid for.
"It has meant that very few parents receive truly 'free' childcare and has ultimately pushed up prices for non-funded hours."