Prime Minister Tony Abbott says embattled Speaker Bronwyn Bishop is on “probation” over her $5227 helicopter flight amid calls for her resignation.

Speaking to reporters in Sydney on Monday, Mr Abbott said he understood the backlash over the Speaker’s decision to take a luxury helicopter from Melbourne to Geelong for a liberal party fundraiser last year.

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But the Prime Minister has knocked back calls for the Speaker to stand down, labelling Mrs Bishop’s actions as an acceptable error of judgement.

“Bronwyn is, I think, very, very contrite about this.

“She will learn a very salutary lesson, a very, very salutary lesson.”

“But like everyone who has done something like this, inevitably, for a period of time, they are on probation.”

The comments come as Opposition Leader Bill Shorten called for the prime minister to sack the speaker after she refused to say sorry for claiming the flight on expenses.

She said paying the money back was an apology in itself.

Quizzed by reporters after an Anzac Centenary event in Sydney on Sunday, Ms Bishop also said she felt no particular pressure to resign.

But she was annoyed when asked to explain the difference between her case and that of Peter Slipper, who stood aside as Speaker during the Gillard government as an independent MP when cab chargers of some $900 were investigated.

“Totally a different matter all together and you know it,” she retorted.

The helicopter trip and other expense claims are now under investigation by the Department of Finance.

Mr Shorten said this has now become a test for Tony Abbott’s leadership who has so far stood by his hand-picked Speaker.

“Tony Abbott has to ask Mrs Bishop to stand aside,” he told reporters in Melbourne. “He can’t dismiss this as … village gossip. It’s this sort of arrogance which turns Australians off politics.”

Ms Bishop wasn’t getting much support from former Liberal MPs either.

John Hewson, who was Liberal leader when Ms Bishop was a senator two decades ago, said she set a pretty tough standard in those days for accountability and transparency, but is now “ducking and weaving” now that the same standards are being applied to her.

“It’s amazing how history bites you in the bum,” he told Sky News.

Former treasurer Peter Costello said she should have never taken the flight.

Treasurer Joe Hockey, who was the first minister to suggest the helicopter ride “failed the sniff test”, said the Speaker had recognised she made an error of judgment and was co-operating with the Department of Finance.

“This has sucked up too much oxygen for the nation over the last few days,” he told Network Ten. “We need to get on with the issues that matter to people.”

Government frontbencher Greg Hunt agreed with the Speaker that her refund of the flight was as good as an apology but conceded he would apologise for any error he made.

Greens Senator Lee Rhiannon said the debacle was a “weeping sore” for the Abbott government and should be investigated by the Australian Federal Police.

– with AAP