They were paused during last month's five-day lockdown and Daniel Andrews said more research is needed before that changes.

"We've asked our medical experts to look at what the impacts of (virus) variants of concern are on the risk profile in our hotels," Mr Andrews said on Thursday.

"When that work is completed, and when they can satisfy me that we can have a system where we have the lowest possible risk, then flights will start again.

"The inconvenience involved in that, I think, pales into insignificance when you think about ... a very easily transmitted virus, a changing virus, changing challenge, and the prospect of further lockdowns. I want to try and avoid that at all costs."

Mr Andrews also confirmed the hotel quarantine workforce would be retained, saying it would cost a lot more to "start from scratch".

Meanwhile, Australia's maritime union says Victoria is missing the boat on its coronavirus testing at ports.

The Maritime Union of Australia has warned that the introduction of mandatory testing for some wharfies - but not sailors arriving from international ports - risks a repeat of the state's hotel quarantine disaster.

"Testing waterfront workers seven days after boarding a vessel, rather than the international seafarers arriving from foreign ports, is like breathalysing the barman instead of the drink driver," said MUA Victoria deputy branch secretary David Ball.

The union said Victoria is the first state to introduce mandatory tests for wharfies and other workers at ports of entry.

While he does not oppose testing port workers, Mr Ball wants national testing of all international seafarers as they arrive at Australian ports.

"Once Australian maritime workers have been infected with COVID, it is already too late, with those workers potentially spreading this virus to family, friends, coworkers, and the broader community," Mr Ball said in a union statement.

"If testing all international airline arrivals is possible, then there is no reason the same model can't be implemented for the international shipping industry.

The union said container terminal operators had also raised concerns with the state government, citing "significant flaws" in the new testing regime.

MUA assistant national secretary Adrian Evans said the current biosecurity system at ports is "fundamentally flawed", leaving dock workers to ensure infections do not reach the community.

"There has not been a single case of vessel to shore virus transmission in any Australian port due to the robust COVID protocols implemented across the industry," he said.

Victorian Health Minister Martin Foley said seafarers had to be tested if they left their ships.

But he added if they stayed aboard, it was outside the state's jurisdiction.

"If you don't get off a cargo or port ship, you firstly don't fall under Victorian jurisdiction. Our ability to compel you to do anything is non existent. That's an issue for the federal government," he said.

Victoria has had its sixth-straight day without a new coronavirus case, with 19,133 tests in the 24 hours to Thursday morning.

There are seven active Victorian cases, one less than Wednesday.

Australian Associated Press