Colbeck made the startling admission while fielding questions about yet another outbreak in Victorian aged care homes, which has exposed more failings in the federally regulated sector.

At least one aged care resident and two staff have tested positive for coronavirus, forcing four facilities into high alert or lockdown.

The Morrison government is seeking advice on whether to mandate vaccines for all staff.

It is also under pressure to explain why it lifted a ban on employees working at multiple facilities, which was imposed after a coronavirus outbreak led to more than 650 deaths in aged care.

Colbeck said as far as the government was aware, almost 40,000 aged care workers had received both doses of their vaccines.

But he has no firm idea how many aged care staff have been inoculated.

“There are a range of different options that are available for staff and we are asking the aged care providers who hold the data to report that information back to us,” Colbeck told ABC radio on Tuesday.

“We don’t have the consolidated data.”

Victoria has recorded three new locally acquired coronavirus cases overnight, as hopes of emerging from the state’s seven-day lockdown on time are starting to fade.

The Health Department on Tuesday confirmed a total of nine locally acquired cases, though six of these were already reported by Acting Premier James Merlino on Monday.

It brings the total number of active cases in the outbreak to 54.

Some 42,699 Victorians were tested in the 24 hours to Tuesday morning, while 20,484 were vaccinated.

There are now more than 300 exposure sites linked to the outbreak and 4000 close contacts self-isolating, of which about 80 per cent have returned negative tests.

Of greatest concern to authorities are three cases linked to an aged care facility in Melbourne’s northwest.

Colbeck has asked aged care providers to report the figures alongside their data on flu vaccinations.

Colbeck said the government was “comfortable” with the vaccine rollout in aged care.

He also defended the delay in reimposing a ban on aged care workers moving between multiple sites.

“It’s actually illegal to inhibit how somebody earns a living, particularly someone who is working in a casual circumstance,” Colbeck said.

“So what we’ve done, in conjunction and co-operatively with the Victorian government, is instituted a ‘one worker, one site’ program where once there’s a hotspot declared.”

Despite Victoria’s concerning outbreak, the rule wasn’t reinstated until the Commonwealth designated Melbourne as a coronavirus hotspot on Thursday.

Health Minister Greg Hunt said about 4.7 per cent of aged care staff had worked across multiple sites as he stressed the importance of flexibility in periods without outbreaks.

He said case numbers were the main factor in determining whether the single-site rule was in place.

Labor’s health spokesman Mark Butler was scathing of the decision to lift the ban in November.

“This latest outbreak in aged care is a direct result of Scott Morrison’s gross negligence and dangerous complacency,” he told reporters in Canberra.

Hunt said a vaccinated 99-year-old woman, who is now in hospital, had contracted the disease at the Arcare home in Melbourne’s west but had not shown symptoms.

A second resident, 95, has been retested on medical advice.

Of Australia’s 910 coronavirus deaths, 685 have been aged care residents.

More than 4.2 million vaccine doses have been administered, a target the government initially set for March.

Health secretary Brendan Murphy, Chief Medical Officer Paul Kelly and Senator Colbeck are set to face questions about the outbreak during Senate estimates on Tuesday.