It comes after opposition foreign affairs spokesman Simon Birmingham questioned the Department of Foreign Affairs and Trade in November's Senate estimates following intense criticism over its drawn out passport wait times.

Recently published questions on notice reveal 1.2 million routine passports were issued between June 1 and November 29 this year, but only 20 per cent were processed within the 10 business day target.

Similarly, more than 240,000 priority passport applications were received in the same June to November period, with one in five not arriving within the promised two business days.

"All customers affected by this would be entitled to receive a full refund of the priority fee," DFAT said.

Nearly $1 billion will be poured back into the federal government's coffers from passport fees this financial year.

DFAT raised almost $355 million from passports between July 1 and November 2 this year, with an additional $974 million projected the end of June 2023.

READ MORE:

All revenue from the passport applications have been returned to the consolidated revenue fund which is where all moneys raised by the executive government of the Commonwealth is allocated.

The department faced significant challenges earlier this year, after receiving record numbers of passport applications due to restriction-free travel opening for the first time since the pandemic in 2020.

DFAT graduates were brought over to the passport office to deal with the surge in applications, which The Canberra Times understood was taken to the Community and Public Sector Union, as there were "concerns about being deployed out of their graduate year".

Extra staff were also deployed from Services Australia to manage the backlog in applications during the peak in July.

The central welfare agency had 120 staff redeployed to deal with applications at its peak but reduced to 43 public servants by November 18.

About 1855 extra staff were employed under the Australian Passport Office since June 2022 and as of November 18 there were 2456 staff working in the office.

The Australian Passport Office also revealed passport demand is expected to "remain volatile" for the next 12 to 24 months.

In November 2021, the department predicted demand to peak at 280,000 applications per month in either March or April 2022.

The Omicron variant, however, delayed this peak, which was reforecast to hit 300,000 applications in October 2022.

By mid-2022, passport demand hit an early peak following the federal election, which the department described as "sooner than expected" due to changes in traveller behaviour and industry offerings.

"APO continues to review and refine its modelling, including working closely with domestic and international partners to better inform our forecasting assumptions and approach," the department said.