"People do it all the time," says Mr Corkery, a Liberal Party donor.

As far as Mr Corkery remembers, the $795,000 Main Beach apartment was advertised in the windows of the Ray White office at Main Beach, on a billboard in front of the building and online. The auction, he says, was held at 10am or 11am in the apartment itself. (The Ray White office did not answer calls on Saturday.)

Under Queensland law people purchasing at auction must pre-register before bidding with a drivers licence or passport, and a utilities bill, but as Mr Corkery says, that can be done quickly before the auction takes place.

It is possible that all the five trips the Health Minister billed to the taxpayer during the months around the time of the purchase were all legitimate work trips, too.

That the purchase of the property was "impromptu" is crucial to Ms Ley's defence to her claim for reimbursement for the travel to the Gold Coast.

According to Howard Whitton, an ethicist and visiting fellow at the University of Canberra who helped then-senator John Faulkner formulate the document that evolved into the standards of ministerial ethics, understanding Ms Leys' purpose of travel is crucial in determining if she complied with the complicated guidelines, regulations and standards that govern how ministers spend public money.

At the heart of the matter, he says, is the simple principle that in her ministerial duties every decision Ms Ley makes and every dollar she spends must be in the public interest.

In the past, he says, ministers and MPs have sought to get around this principle by arranging official events to coincide with personal business at locations they wanted to visit.

Stuart Robert was forced to resign after he tangled public and private travel to China while serving as assistant minister for defence in 2014.

Even after the then speaker of the house, Bronwyn Bishop resigned after her profligacy with travel entitlements was revealed, the former prime minister Tony Abbott was criticised for taking a tax-payer funded VIP jet to Melbourne to attend a Liberal donor's birthday bash and, he said, conduct some official business.

"Mr Abbott had other work-related engagements in Melbourne on Sunday 22 March, 2015," a spokesman said in a statement at the time. "All travel was undertaken within the rules."

Asked if the practice of arranging official business to coincide with private trips so as to claim public funding for them should be a sackable offence, Mr Whitton said it was a matter for the Prime Minister, Malcolm Turnbull, "though many Australians might think so".

After Ms Bishop's resignation, Mr Turnbull toughened ministerial standards guidelines, which include the following words: "Although their public lives encroach upon their private lives, it is critical that Ministers do not use public office for private purposes ...

"Ministers are expected to conduct all official business on the basis that they may be expected to demonstrate publicly that their actions and decisions ... were taken with the sole objective of advancing the public interest ...

"Ministers must be scrupulous in ensuring the legitimacy and accuracy of any claim for entitlement to ministerial, parliamentary or travel allowance."

Asked to provide details about the people with whom she met during official business on her trip to the Gold Coast, a spokesman said, "The Minister met with patients on the Gold Coast, however, because of patient confidentiality and sensitivity reasons she does not intend to provide any more information on this meeting."

An earlier statement by her office echoed that by Mr Abbott when he faced earlier criticism.

"All travel undertaken was in accordance with the rules," it said.