Parents' access to childcare will be dramatically expanded under Labour plans to subsidise extra hours, Jeremy Corbyn will say.
His commitment would see parents pay no more than £4 an hour for extra childcare on top of the 30 hours a week of free provision for all two, three and four-year-olds already promised by Labour.
Poorer parents would get free entitlement to the additional hours, Mr Corbyn will say in his leader's speech at Labour's conference on Wednesday.
Mr Corbyn will say the current "patchy support for childcare is holding back too many parents and families" and set out plans that could benefit more than a million children.
"Universal free high-quality childcare will benefit parents, families and children across our country," he will say.
"It is a vital and long overdue change that will transform people's lives and meet the needs of a 21st century Britain for all."
Under the existing system, working households in England are eligible for 30 hours of funded childcare for infants aged three or four, while some qualifying families can get 15 hours for two-year-olds.
But Mr Corbyn will say it is "free in name only", with only 40% of two-year-olds qualifying and many working parents of older children not getting the 30 hours because of the complexity of the system.
Announcing plans for a shake-up of the system, Mr Corbyn will pledge to drive up the standards of childcare, with higher skill levels and pay rates for workers.
Parents would be able to use a simplified online system to arrange their childcare, while over two years there would be a shift to a graduate-led workforce.
Mr Corbyn will say: "Opportunity matters most in the earliest years of life. It is a crucial time to open up children's life chances.
"Driving up standards of childcare will make that vital difference for millions of our children."
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