New Prime Minister Jacinda Ardern says she can deliver a free year of study by 2018.

Prime Minister Jacinda Ardern has reaffirmed a campaign commitment to young people on her first day of the job: They can start their tertiary study next year for free.

Labour's three years free policy would eventually grant three full years of free post-secondary study - whether that be at a university or on another course - to anyone who hasn't studied before.

The policy would be phased in over several years, but on the campaign trail Ardern flagged the first year of free study as being in 2018.

Getty Images Ardern speaks to high school students an hour after being sworn in as prime minister. She's planning to grant them a free year of study in time for next year.

The second year would kick in for 2021, and the third 2024.

READ MORE: Jacinda Ardern's new government sworn in

On Thursday, as a crowd of young people chanted behind her, Ardern said prospective students could start planning their free year of study with certainty now.

"We're committed to that policy, absolutely," Ardern said.

"We knew it would come with some difficulties rolling it out immediately. It's possible but we will need to work quickly within the first 100 days."

Officials were already working on advice about the options to get it done that quickly.

GETTY IMAGES New Education Minister Chris Hipkins and Housing Minister Phil Twyford. Twyford said the long term solution is increased supply.

New Education Minister Chris Hipkins didn't want to comment before having seen the advice, but said he would update media on the plan early next week.

Ardern raised the prospect of a "mini-Budget" to implement policy priorities within the next few months.

"Some of our 100-day commitments we really need to act urgently on if we are to get the legislation through on time."

"There are elements of it that could well be wrapped into a mini-Budget."

A budget would allow various departments to make urgent bids to Treasury for appropriations.

Labour also promised a $50 increase to student allowances and student loan living costs, as well as restoring eligibility for the student allowance to postgraduate students and those studying long courses such as medicine.

To be eligible for a second year of free study - which won't be available until 2021 - students would need to pass more than half of their courses in the first year.

Labour's pre-election costings, which were verified by BERL, put the cost of the policy at $340m per year, along with $270m per year for the boosts to student support.

There was a stoush over costings in 2005 when Labour introduced its interest-free student loan policy, and rejected a Treasury costing it saw as too high.

That policy was set up - also rapidly - by still allowing IRD to rack up interest charges throughout the year, but to then write them off near the end.

It's understood that some kind of writeoff plan could be one of the options on the table for this new policy too.

Outgoing tertiary education minister Paul Goldsmith described the policy as a far too expensive on the campaign trail.

"It isn't fair to ask hundreds of thousands of New Zealanders – who haven't had the benefit of tertiary education – to pay more in taxes just to support those who do."

"For more than 25 years – and successive governments – students have made a modest contribution toward their study, while the community picks up around 80 per cent of the cost. National thinks this is fair."