The Foreign Secretary, who is seen as a frontrunner to succeed Mr Johnson if he is forced to quit, stressed that there was “no leadership election”.
She replied: “The Prime Minister has my 100 per cent support. He is doing an excellent job. Britain was one of the first countries to roll out the Covid vaccine.
“We’ve had a very successful booster programme. We’re now able to open up our economy again in Britain and we’ve got one of the fastest-growing economies in the G7.
“And the reason that we are here in Australia is working with our very close partners, to advance freedom and democracy around the world, and to protect our country.
“I want the Prime Minister to continue as long as possible in his job. He is doing a fantastic job. There is no leadership election.”
Senior civil servant Sue Gray is due to report early next week into a string of parties in Downing Street when Britain was in lockdown or under other Covid restrictions.
Loyalist MPs have rallied around the Prime Minister but seven Tory backbenchers have gone public calling on him to go.
Senior Brexiteer MP Steve Baker said on Thursday that he believed Mr Johnson was in “checkmate”.
If 54 Tory MPs submit letters of no confidence to Sir Graham Brady, chairman of the 1922 Committee of backbench Conservative MPs, it would trigger a vote in Mr Johnson’s leadership.