But it could have been less of a hit to the taxpayers' pocket if Western Australia had not had such a hard border lockdown and flights so hard to access.

Official figures released on Monday showed Assistant Minister to the Prime Minister Ben Morton spent $20,370 on travel over three months.

The bill reported to the Independent Parliamentary Expenses Authority was higher than any other WA-based minister, including Finance Minister Mathias Cormann.

The expenses included 15 consecutive nights in March and April spent in Canberra, and a further 32 nights across May and June working alongside Mr Morrison to respond to the pandemic.

A spokeswoman for Mr Morton told AAP the assistant minister had taken on temporary responsibilities for the Australian Public Service as well as his role in assisting the prime minister.

"(Mr Morton) has been required to spend a significant amount of time in Canberra to support the Prime Minister and Cabinet in the government's response to the coronavirus pandemic," she said.

"This has resulted in greater than normal nights based in Canberra, away from his home in Perth.

"During this time the ability to travel between Canberra and Perth has been severely restricted, including as a result of reductions in flight availability."

Nationals MP David Gillespie had the highest office administration bill, notching up $142,625 in three months, most of which went on printing and communications.

Australian Associated Press