The Government will plough an additional £4 billion into free childcare for one-and-two year olds in England - but Labour has warned this will crash the existing system.
Under plans to be announced by Chancellor Jeremy Hunt, parents of children in this age bracket will get an extra 30 hours a week.
The Tories will also steal Labour's plan to offer primary school pupils access to breakfast clubs, as well as offer extra after school provision.
But former shadow business minister Stella Creasy branded the massive expansion of free childcare "economically illiterate" and warned there would not be enough capacity to provide the promised hours.
Under Mr Hunt's plan, it is understood, there will also be an additional injection of cash for three-year-olds, it is understood, although the amounts are not currently clear.
The measures are set to be delivered as part of Mr Hunt's 'back to work' budget, which the Treasury says will address labour shortages across the UK.
Mr Hunt Hunt will unveil his first Budget as Chancellor tomorrow amid a backdrop of mass industrial action, sky-high inflation and a cost-of-living crisis.
Ms Creasy said: "Taking away funding from kids over three to offer hours for kids under that age without funding those hours fully will not only cause the existing childcare system to crash but also penalise any family with a child who isn’t a toddler.
"This is as economically illiterate as help to buy where the Government policy pushed up demand without addressing supply and so ended up making housing cost more for first time buyers not less."
And the Labour MP continued: "If we want families to be able to work and care for their kids – and so pay the tax that covers the costs - we need to fund it from the end of parental leave until a child no longer needs afterschool care – this system could well end up costing parents more because it fails to recognise children's age."
A source told The Mirror that the childcare boost, first reported by The Guardian, will form part of the package to be delivered tomorrow.
Officials hope it can help parents back into work and in turn boost growth, and it has been described as Mr Hunt's 'rabbit in a hat' moment.
Childcare providers will also receive a higher rate, it is believed.
There will also be extra funding for schools from next September to provide wraparound childcare.
Rishi Sunak is expected to sign off on the childcare plan today ahead of Mr Hunt's address at 12.30pm in the Commons.
Mr Hunt is expected to announce that people on Universal Credit will be able to claim back more cash for childcare.
The Institute for Fiscal Studies (IFS) says that to account for rising costs, the amount parents can claim would rise to £1,200 for one child - up from £646 - or £2,000 for two, rising from £1,108.
The Tories are under huge pressure to act after Labour said childcare would be a key part of its manifesto.
Shadow Education Secretary Bridget Phillipson blasted the Government for "failing families" with a chaotic childcare offer that prices parents out of the workplace.
She said it was time for a complete overhaul of the "complex and confused" system - and "bolting on" more hours would not fix issues of provision and cost.
Parents are forced to grapple with a mish-mash of provision, which includes 15 free hours of childcare in term time for all three and four-year-olds.
Children of working parents can get 30 hours per week if they meet eligibility rules, while some two year-olds qualify for 15 hours if their parents are
In a speech to the Onward thinktank in London, Ms Phillipson said: "Support for childcare is at once inadequate and delivered through too many systems: complex and confused.
"The cost of childcare is pricing parents out of jobs they love, when it is available at all."
She warned that the Government is underfunding early years providers to deliver the free hours policies - pushing many to brink of collapse and leaving parents facing "extortionate costs".
