Families have been promised access free or subsidised preschool for children as young as three if Labor wins government at the next federal election.

Key points: Labor's proposal would give three-year-old children access to 15 hours a week of preschool education

Labor's proposal would give three-year-old children access to 15 hours a week of preschool education It would be free for children attending state-government-run preschools, or subsidised for those getting preschool education at private childcare centre

It would be free for children attending state-government-run preschools, or subsidised for those getting preschool education at private childcare centre Plan to cost $1.75 billion over three years from 2019, but change for three-year-olds would not kick in until 2021 school year

Under the proposal, children would be able to access 15 hours a week of education in the two years before going to primary school.

It would be free for three-year-olds able to attend state-government-run preschools, while the Government would provide an extra subsidy for three-year-olds obtaining preschool education at a private childcare centre.

Commonwealth funding for early childhood education currently only supports four-year-olds.

Labor early childhood education spokeswoman Amanda Rishworth said the plan would be the biggest-ever investment in early childhood education, adding it would be a major social and economic reform.

"We know that children who get high-quality early education for the two years before school do better when they start school and these benefits are long lasting," Ms Rishworth said.

According to figures from the Parliamentary Budget Office, which costed Labor's plan, the total cost over a decade would be $9.8 billion.

The full early education plan would cost an estimated $1.75 billion from 2019 to 2022, but the change for three-year-olds would not kick in until the beginning of the 2021 school year.

Impact on underlying cash balance ($m) 2019-20 2020-21 2021-22 Total over forward estimates period Four-year-old preschool subsidies -$132m -$446m -$463m -$1.041b Three-year-old preschool subsidies - -$149m -$499m -$648m National Quality Agenda -$20m -$20m -$20m -$60m Total -$152m -$615m -$982m -$1.749b

*Note: Forward estimates cover four financial years from the current year. For this breakdown, the 2018-2019 financial year has been costed at zero because Labor is not in government.

Opposition Leader Bill Shorten said Labor would fully fund the commitment through changes to negative gearing.

Shadow Treasurer Chris Bowen said while the initiative had a significant price tag, it would be a worthwhile investment in the long run.

"[We know], through study after study after study, around the world, the return on this investment is very significant. The more you invest in early childhood education, the better the results right through school — and of course then on into life," Mr Bowen said.

Federal Education Minister Dan Tehan criticised Labor's plan by saying it was important to get four-year-old preschool attendance rates right before bringing younger children into the mix.

"This is a big headline number, it's big spendage by Bill Shorten, which means that your taxes will go up," he said.

"All it shows is that Labor will be a big-spending, big-taxing government.

"We have been focusing on four-year-old kinder, we want to make sure that we get attendance levels right.

"We've got enrolments but we're not getting children into four-year-old kinder at the rates that we want, especially when it comes to those from low-socio-economic areas, those from rural and remote areas and those from Indigenous communities."

'Massive change' for parents

Mr Shorten said Labor's plan would give Australian children access to at least 15 years of continuous education, from the age of three to 18.

"All the educational experts have made it very clear that [a] little child's development up to the age of five is very important," he said.

"It'll also help parents with the cost of paying for preschool, and I think it'll make really a massive change.

"It's reimagining childcare into early childhood education, and I think Australia, parents and the kids will all be the winners."

Preschool enrolment rates at age three (per cent) Country Preschool program Child care Total UK 100 100 Israel 100 100 France 99 99 Norway 95 95 Spain 95 95 Korea 92 92 New Zealand 89 89 Australia 21 47 68 Chile 49 6 56 Source: Education at a glance 2017: OECD indicators.

According to Australian Bureau of Statistics data published in February, last year there were 339,243 children aged four or five enrolled in preschool across government and non-government preschools as well as long day care centres.

The estimated number of four-year-old and five-year-old Australian residents was 640,915 — meaning about 53 per cent of those children were attending preschool at the time.

Ninety-five per cent of those in preschool were enrolled for at least 15 hours per week.

But Labor argues Australia is lagging behind other countries in early education for three-year-olds, pointing to the UK and New Zealand, which both have near-universal preschool for children that age.

In a speech at Monash University announcing Labor's plan, Mr Shorten cited these examples as well as Norway, Ireland, France, South Korea and China.

"The number of Chinese three-year-olds in preschool is greater than the entire population of Australia," Mr Shorten said.

"But in Australia, only 15 per cent of Australian three-year-olds are attending preschool.

"So we are already miles behind the nations I have mentioned. We are well below the OECD average of 78 per cent."