The party said a government led by Jeremy Corbyn would invest £1bn into reopening the 1,000 centres that have closed under the Conservatives and expand government-funded childcare to include all two to four-year-olds.
Currently, parents can apply for 15 hours of free childcare for all three to four-year-olds. Working parents on lower incomes can request a further 15 hours on top of this.
Labour said it would spend £4.5bn on expanding the entitlement to all children aged three and four and extending it to all two-year-olds.
But experts said questions over how the policy will be funded would "strike fear into the hearts of many providers".
Mr Corbyn will announce the pledge during a visit to Leeds on Saturday alongside Angela Rayner, the shadow education secretary.
Ahead of the visit, the Labour leader said: "The Conservatives are failing a whole generation of children. Labour will deliver the real change Britain needs.
“Parents are struggling to afford the childcare support they need, while many children are going hungry and growing up homeless.
“Labour will open a Sure Start centre in every community and fund 30 hours’ free childcare for all two to four year olds to unlock the potential of every child.”
House of Commons Library analysis commissioned by Labour found that extending free childcare to 30 hours a week would save parents who are currently only entitled to half that amount more than £2,500 a year.
And extending the provision to two-year-olds would save the average parent more than £5,000 a year.
The change would help more than 880,000 three-and four-year olds and over 500,000 two-year-olds over the next five years.
Labour said childcare costs have risen twice as fast as wages since 2010, and more than three times more in some parts of the UK.
Ms Rayner said: “Investment in the early years can transform the lives of children and their families across this country, just as the last Labour government transformed mine.
“The Tories have slashed funding for Sure Start leading to a loss of 1,000 centres, while their so-called free childcare offer locks out those families most in need of support.”
Sure Start centres were introduced by New Labour to help parents access a range of services for their young children, including education, healthcare and parenting advice.
They were credited with helping to bridge the gap between children from disadvantaged backgrounds and their more privileged peers, but budgets for the centres have been cut by almost £1bn since 2010.
Experts warned that Labour's promise to open 1,000 new Sure Start centres would need to be properly funded if it were to have a positive impact.
Neil Leitch, chief executive of the Early Years Alliance charity, said: “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.
“This is an already unsustainable situation and so the last thing we want is more of the same: any new policy like this needs to come with a firm commitment to sort out the current funding mess first.”
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