About 700,000 three and four-year-old children will get a minimum of 15 hours a week of preschool or kindergarten if Labor wins the next federal election.
Under the $1.75 billion plan, preschool will be extended to three-year-olds, giving children 600 hours of subsidised early childhood education a year.
But Prime Minister Scott Morrison says it's unclear how many extra hours Labor has funded.
Opposition Leader Bill Shorten announced the policy in Melbourne on Thursday, making a pitch to parents ahead of the next election, due by May.
"All of the results show that children who are able to get two years of preschool education just do better in school," he told reporters at a childcare centre.
Extending early childhood education to three-year-olds would bring Australia in line with the United Kingdom, New Zealand, France, China and other countries.
"The rest of the world has been moving ahead and been implementing universal access for preschool to three-year-olds. What we want to do is give Aussie kids the same chance," Mr Shorten said.
Labor will fund the 10-year, $9.8 billion plan by reining in tax concessions, including negative gearing and dividend imputation.
Mr Shorten said stripping back "unfair" features of negative gearing would ensure more was spent on early childhood education than tax subsidies for property investors.
But Mr Morrison said there was a significant hole in Labor's costings, with $1.75 billion unable to cover both three and four-year-olds.
"They actually don't seem to have funded anything for three-year-olds at all," the prime minister told reporters.
"They can't decide whether the funding is over two years or four years.
"They haven't explained what the support of the states and territories are going to be for this."
Mr Shorten said there is some money already locked in the budget for four-year-olds to get funding, which will run out in 2019.
Victorian Premier Daniel Andrews announced a $5 billion package for preschool on the same day, ahead of a state election less than two months away.
He said if Labor won the federal election money would be freed up from the Victorian plan, which will provide every three-year-old with 15 hours of subsidised kindergarten from 2020.
"What state premier would want to stand in the way of making sure that three and four-year-olds get universal access?" Mr Shorten said.
Early childhood education advocacy groups welcomed Labor's plan.
"There evidence is clear that children with access to two years of preschool improves educational and wellbeing outcomes for young children," Early Childhood Australia chief executive Samantha Page said.
Australian Associated Press