Labour is promising to open 1,000 new Sure Start children’s centres in England.
Party leader Jeremy Corbyn says he would invest £1bn in the early years centres, as part of a package of childcare support.
The Lib Dems will promise subsidised childcare for working families from when children are nine months old.
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.
On a visit to Leeds with shadow 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.
According to a report from the Sutton Trust last year, up to 1,000 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.
Ms Rayner said the extra support for early-years education could “transform lives”.
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 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”.
Layla Moran, the Lib Dem education spokeswoman, said it would support families as they “juggle the demands of modern life, working and parenting, by giving them more choice over how they organise their lives and improve social mobility with early-years education”.
More on the election
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.
Early Years Minister Nick Gibb said: “Labour’s plans to abolish Ofsted would leave these centres without anyone properly checking your children are safe.”
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.”