International students are unlikely to return to Victoria at pre-pandemic levels until 2022, according to the state’s treasury department.

The state’s big-spending budget, unveiled last week, rests on a number of key assumptions about the COVID-19 pandemic, including the reopening of international borders by the middle of 2021.

Treasury Secretary David Martine conceded on Tuesday it will be a “slow reopening”, with international students unlikely to return to the state until the start of 2022.

“We’re not expecting to see a significant return of international students until the year after,” Mr Martine told parliament’s public accounts and estimates committee.

International education has been Victoria’s largest services export industry for more than a decade, generating $13.7 billion in revenue in 2019 and employing almost 80,000 people.

Victoria hosts about a third of Australia’s onshore international students.

It comes as the first charter flight of international students touched down in Darwin on Monday as part of a pilot program to bring students back to Australia.

Two similar programs in Adelaide and Canberra were put on hold due to the second wave of the pandemic in June.

Mr Martine said treasury expects Victoria will return to “COVID normal” by the end of 2020.

It also assumes any further outbreaks in Victoria and interstate are contained and do not lead to any further city or statewide restrictions.

But unlike the federal budget, Victoria’s doesn’t forecast when a COVID-19 vaccine will be made available.

“There is certainly positive views about vaccines, but they’re going to take a while to spread through the community,” Mr Martine said.

“Even if they’re available at the start of 2021, by the time people get vaccinated and spread through, not just here in Australia but around the world, that’s going to take some time.”

The budget is intended to fast-track the state’s recovery out of the coronavirus crisis and includes about $80 billion in infrastructure spending and $49 billion in new stimulus measures.

As a result, debt is expected to soar to $154.8 billion by 2023/2 – about 28.9 per cent of the size of Victoria’s gross state product.

International credit agencies are wary about the state’s record level of debt, with S&P warning there’s of a “one-in-two likelihood that we will lower our rating on Victoria”.

Treasurer Tim Pallas said the government was putting the interests of Victorians “first and foremost”.

“Whether or not we keep a AAA credit rating is beyond my control. But we will continue to manage our budget in a AAA-rated responsible approach,” he told the committee.

Interest will increase between $1.9 million and about $10 million per year if Victoria’s credit rating was to drop to the second-highest level of AA+.

“The rates are incredibly low at the moment and the spreads are even lower,” Mr Martine said.