In short: 

Shadow transport minister Bridget McKenzie has confirmed she failed to declare 16 free flight upgrades between 2015 and this year.

The revelation came after she conducted an audit of her flight history, amid a wider debate over political travel perks.

What's next?

The previously undisclosed upgrades will now appear on Senator McKenzie's register of interests. 

Coalition frontbencher Bridget McKenzie has admitted she failed to declare 16 flight upgrades over several years.

The shadow transport minister's admission comes a week after she claimed to have never received any complimentary airline upgrades, amid a wider debate about political travel perks.

The senator has now disclosed she was upgraded to business class on three domestic Qantas flights this year and last year, upgraded five times on Qantas flights between Australia and New Zealand between 2016 and 2018, and on eight more flights between 2015 and 2019 with both Qantas and Virgin.

In a statement, Senator McKenzie apologised for her error.

"Deficiencies in disclosing these matters do not meet the expectations of the Australian people and the parliament and were an oversight on my part, and for this I apologise," Senator McKenzie said.

"I have and will continue to prosecute the Albanese Labor government's failure to ensure greater competition in the aviation sector on behalf of all Australian travellers."

Under parliamentary rules, all MPs and senators are required to declare any free or upgraded travel and gifts over the value of $300 within 28 days of receiving them.

Questions over what influence airlines wield over politicians through the perks they provide dominated debate last week, after author Joe Aston published claims that Prime Minister Anthony Albanese solicited upgrades from former Qantas chief executive Alan Joyce.

It sent politicians from all sides scrambling to check that their own declarations were above board and it also sparked calls for a review of how the system operated.

Mr Albanese has rejected the claim that he requested upgrades directly from Mr Joyce and said any other upgrades had been declared on the register of interests.

Coalition says failure to disclose upgrades different to claims about PM

Senator McKenzie had been among the loudest voices calling for the prime minister to explain his flight history, as the Coalition has called for the prime minister to refer himself to the corruption watchdog.

The Coalition frontbencher initially claimed she had never received an upgrade, but later backtracked and said she should not have been "so emphatic" about her flight history.

"I don't probably believe I should be subjecting other people to standards I'm not prepared to subject myself to," she told ABC's RN last week.

Senator McKenzie then said she had written to Qantas, Virgin and Rex to check whether she had received any upgrades that had not been disclosed.

Earlier on Wednesday, Shadow Treasurer Angus Taylor said his colleague should correct the record if it was revealed that Senator McKenzie failed to declare the perks.

But he also sought to draw a distinction between the failure to declare upgrades and the allegation that the prime minister sought them out while he was transport minister.

"Any upgrade, like any benefit given to a politician, needs to be declared … If there's been an error on that, then it should be corrected," he told ABC Radio National.

"But that's completely different from a circumstance where the minister responsible for this area reaches out, either directly or through their office, to lobby for an upgrade for personal use."