Scott Morrison has refused to rule out extending early childhood education to three-year-olds but attacked Labor’s $9.8bn 10-year promise for lacking detail about cooperation with the states.

On Thursday Bill Shorten unveiled Labor’s policy to permanently grant universal access to preschool or kindergarten for three and four-year-olds for 600 hours a year, while the Victorian Labor government announced it will also guarantee 15 hours a week of preschool for three year olds.

At a cost of $9.8bn over 10 years, federal Labor will extend preschool funding for four-year-olds – currently only funded to the end of 2019 – and introduce universal early childhood education for three-year-olds from the start of 2021.

The education minister, Dan Tehan, said the plan was “ill-thought through and rushed” and amounted to “big spending by Bill Shorten” that will contribute to higher taxes.

“There’s no agreement with the states and territories about what proportion the commonwealth government will fund, what proportion the states and territories will fund,” he told ABC Radio.

Tehan said the Coalition was “focusing on [pre-school] for four-year-olds”, attempting to boost low attendance rates among low socio-economic status, rural, remote and Indigenous children.

Early childhood education for four-year-olds is currently funded two-thirds by the states and one-third by the commonwealth.

At a press conference in Sydney, Morrison said the detail of Labor’s announcement was “all over the place” because funding “would have to be matched by the states and territories”.

“It is one thing to invest money, but taxpayers expect results for it and when we go into partnerships with the states and territories, we expect them to deliver results and we want to see improved results in that area from the investments we’ve already been making and we will be considering further investments in that area in the future.”

Asked if the Coalition was open to extending early childhood education to three-year olds, Morrison replied “we’re open to a lot of these things [but] you’ve go to pay for these things”.

Morrison said the government is committed to universal access to preschool because it had funded it for four-year olds “for the last five years”.

He said funding is “secure all the way to the end of 2019 and we will go through this process through … the budget as usual … and continue to deliver the funding each and every year”.

At a doorstop after the speech, Shorten said the policy was about “making sure that our three and four-year-olds get the best start in life”.

Asked about whether the states and territories would sign up, Shorten said that “plenty of states are already thinking about it” and that Victoria’s example showed that states “will get on board”.

In July the Australian Capital Territory announced it would extend 15 hours a week of preschool education to three-year-olds, joining New South Wales, which was the first state to announce such a policy.

On Thursday the Victorian government announced it would spend $5bn over the next decade to deliver 15 hours of pre-school for three-year-olds, beginning in 2020.

The Victorian premier, Daniel Andrews, said its costing was based on “the current policy settings of the Liberal federal government, so we’re doing it all”.

He said if Labor won the federal election, Victoria would partner with the commonwealth, share costs and some of the $5bn funding would be invested elsewhere.

Shorten said that only 57% of Australia’s three-year-olds were in long day care or preschool, and just 15% were in preschool compared with the OECD average of 78%.

France, New Zealand, the United Kingdom, Norway and Ireland all have universal early childhood education for three and four-year-olds, with the UK moving towards 30 hours a week, double Labor’s offering of 15 hours.

Federal Labor has defended estimates the policy will only cost $1.75bn over the forward estimates, saying the parliamentary budget office has costed it.

The lower cost over the forward estimates reflects the fact no money is set aside for 2018-19 – when Labor is in opposition – preschool for four-year-olds is already funded in 2019 and three-year-olds will not get universal access until 2021.