Tony Abbott has put embattled Speaker Bronwyn Bishop on notice, potentially paving the way for her removal if an investigation into her travel claims finds against her.
With the Speaker copping "a justifiable hiding" over a 100km helicopter flight, she will learn a "very salutary lesson", the prime minister says. Mr Abbott confirmed the Speaker still enjoyed his confidence.
"But like everyone who has done something like this, inevitably, for a period of time, they are on probation."
Labor frontbencher Tony Burke sent a letter to Mr Abbott on Monday afternoon, asking for clarification on what probation entails and how it would impact the Speaker's authority over the House of Representatives.
The finance department is investigating the claims Mrs Bishop made for the helicopter ride from Melbourne to a Liberal Party fundraiser in Geelong, as well as two more recent charter flights to the NSW regional towns of Young and Nowra.
The Speaker already has repaid $5227 and a 25 per cent penalty for the Geelong charter.
"She has certainly copped a justifiable hiding over the last few days," Mr Abbott told reporters in Sydney on Monday as Labor stepped up calls for her head.
He played down criticism Mrs Bishop had not apologised for making the Geelong claim, referring to a couple of long conversations the pair have had over the controversy.
"Bronwyn is, I think, very, very contrite about this," Mr Abbott said.
"She will learn a very salutary lesson, a very, very salutary lesson." Labor leader Bill Shorten says the prime minister needs to show courage and tell Mrs Bishop it's time to go.
"Every day this saga goes on, Bronwyn Bishop's position is increasingly untenable and it would appear that Mr Abbott is digging himself a hole, too."
Senior Labor frontbencher Anthony Albanese warned the issue threatened to dominate parliament when MPs return to Canberra on August 10.
He called on Mr Abbott to replace Mrs Bishop with a senior Liberal MP who better understood parliamentary rules.
Allan Fels, a member of an independent committee that reviewed parliamentary entitlements, insists MPs know they can't claim travel expenses for attending party political events.
But Professor Fels also admits the 2010 review could not adequately refine the rules because there was "a number of slightly tricky boundary problems".
It was well understood and accepted by MPs that they could only claim travel entitlements for parliamentary or electorate business or attending a national conference of their party, he said. Prof Fels said there was an explicit exception in the rules about attending national conferences.
"We took that as meaning that they could not get travel entitlements for party business other than the national conference."
When asked whether Ms Bishop's claim for the helicopter charter was within the rules, Prof Fels said: "If it's a purely political party function then no minister, Speaker or member of parliament can claim travel.
"If it's a function they're attending in their official capacity as clearly official Speaker business then she's probably OK."
