A Senate estimates committee was told on Tuesday there were 32,300 Australians stranded overseas who have put their names forward to the Department of Foreign Affairs and Trade to return.

The figure was 18,800 in late August.

The committee heard DFAT had advised the number would rise as that was the usual scenario in any crisis situation.

Labor senator Penny Wong asked why the number was rising while the government continued to state it was doing all it could to get Australians home.

“The goal as stated by the prime minister was to get people home by Christmas,” Department of Prime Minister and Cabinet deputy secretary Alison Frame said.

She said a multi-agency task force including the acting chief medical officer Paul Kelly had been working on the issue with the states and territories and airlines.

Modelling had been done to get all 4000 of the Australians listed as “vulnerable” home by Christmas, as well as gradually reduce the number of other Australians seeking to return, the committee heard.

A facilitated flight is due to deliver Australians to the Howard Springs facility outside Darwin on October 23.

Extra accommodation capacity would be opened up with the start of the New Zealand travel bubble, Ms Frame said.

Labor frontbencher Kristina Keneally questioned how Tony Abbott had been allowed to leave Australia twice while more than 30,000 were stranded.

Australian Border Force boss Michael Outram said the former prime minister had been given an “auto-exemption” from restrictions because he was travelling for government business.

Mr Outram said Mr Abbott, who has been working as a trade adviser to the British government, qualified as ABF considered foreign government business exempt.

-AAP