The taxpayer footed the bill for Prince Andrew's £16,000 flight to watch golf tournament The Open Championship, figures show.
The Duke of York flew in a private jet from Farnborough, Hants, to Portrush, in Northern Ireland last July, even though there were 13 daily flights from London to Belfast, according to reports.
Following the 60-year-old royal's car crash interview with Emily Maitlis for BBC's Newsnight in November, the Royal Portrush stripped him of his patronage.
The duke was roundly slammed for his failure to apologise for his friendship with late billionaire paedophile Jeffrey Epstein.
The expenditure was detailed in the delayed annual Sovereign Grant Report where the royals reveal how they have spent the annual allowances from the Treasury.
A palace source told The Sun: "He was undertaking a visit on behalf of his patronage. Arrangements in relation to the programme did not enable him to travel by scheduled flight."
Andrew's sister Princess Anne is similarly under fire for a day trip to Rome for a Six Nations match in February as patron of the Scottish Rugby Association which cost the taxpayer £16,440.
A royal source said the charter flight she took was "deemed being most appropriate" in relation to security, as well as "value for money".
Next-in-line to the throne Prince Charles spent £19,100 on a private flight to Aberdeen a day before Britain went into coronavirus lockdown in March.
The travel costs for Prince Harry and Meghan Markle's high-profile family tour to southern Africa last September cost the taxpayer nearly £246,000.
The Duke and Duchess of Sussex took their then four-month-old baby son Archie Mountbatten-Windsor to South Africa on his first royal overseas trip, with the duke also travelling solo to Angola, Malawi and Botswana.
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The flights came to nearly a quarter of a million pounds and were the most expensive royal journey of 2019-2020, according to the royal financial records.
It comes as the Queen faces a £35 million shortfall in funding because of Covid-19 but has vowed to avoid asking the Government for a bailout from taxpayers.
She has promised to look for cost savings and efficiences in the way the Royal Household operates after her senior advisers revealed the full cost of the coronavirus in royal accounts published last night.
A 10-year, £369 million project to refurbish Buckingham Palace is now forecast to run £20 million short because the amount of money the Queen receives from the taxpayer is expected to stand still for the first time at £86.3 million in the next couple of years.