The chancellor will promise to provide 30 hours of childcare a week to parents of one and two-year-olds, Sky News has learned.
The multi-billion pound announcement is set to be made in today's "back to work" budget.
Families with children aged one and two do not currently receive support after parental leave ends and before free nursery hours are offered for three and four-year-olds.
Extending the provision could form a central plank in Jeremy Hunt's pitch of helping with the cost of living and getting parents into work, according to Sky News' political editor Beth Rigby.
UK childcare costs are among the most expensive in the world, with full-time fees for a child under two at nursery reaching an average of £269 a week last year - equivalent to around £14,000 annually.
Last month, the Early Years Alliance told Sky News nursery fees are expected to increase even further, going up by an average of 8% - higher than in previous years.