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 announcement is set to be made in tomorrow's Budget.
Families with children aged one and two do not currently receive support to cover the period 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.
Tory MPs have been pressing the chancellor to make childcare more affordable in the March budget to reduce pressure on families and enable more women to re-enter the workforce.
The chancellor is also expected to change the rules so that parents on Universal Credit are given more childcare and given the funding upfront.
The Treasury is also believed to be planning a cash injection of hundreds of millions into increasing the availability of the 30 hours of free childcare to three to four-year-olds.
The chancellor also plans to loosen staff to child ratios for two-year-olds, which could make the cost of childcare a little cheaper.