Former speaker Bronwyn Bishop wanted to make an immediate apology for the use of taxpayer money to charter a chopper for a Liberal Party event but was told to hold off by Tony Abbott's office, a new book says.

The account, which is being disputed by several sources in the former prime minister's office, is contained in a book by political commentator Niki Savva, The Road to Ruin: How Tony Abbott and Peta Credlin Destroyed Their Own Government.

It cites sources who said Ms Bishop wanted to apologise immediately for claiming travel allowance for the return chopper ride between Melbourne and a golf course near Geelong for a Liberal Party function.

In the end it was 15 days before Ms Bishop made a public apology. Under pressure from Labor and some of her own colleagues she eventually resigned from the speaker's chair.

The story of Ms Bishop's travel claim was originally broken by the Herald Sun newspaper on Wednesday July 15 last year.

Documents filed with the Department of Finance confirmed the then-speaker chartered the helicopter for a return trip between Melbourne and the Clifton Springs Golf Club in late 2014.

The distance by road was estimated to be about 80 kilometres, around 90 minutes by car each way. Instead Ms Bishop claimed $5,227.27 in travel expenses for the helicopter ride.

The day after the story broke Ms Bishop released a statement saying she would pay back the money with an additional 25 per cent penalty, but Labor seized on the spending claim as evidence Ms Bishop should relinquish her position.

Office said saying sorry would admit guilt

According to Savva, sources confirm Ms Bishop wanted to go further and make an apology on Friday to try to kill off the story.

Loading

The book says the message from Kate Raggatt in the Prime Minister's office was to hold off.

On Saturday, four days after the story broke, the book says Ms Bishop was instructed by the Prime Minister's office to make a public statement, but Ms Raggatt advised against specifically saying sorry because it may be construed as an admission of wrongdoing.

The book says Ms Bishop became convinced that further leaks about her travel claims were coming from inside the Prime Minister's office.

It took until July 30 for Ms Bishop to express remorse.

"I am so apologetic to the Australian people for letting them down and I will be working very hard to make sure things are right," she said.

On August 2 she handed in her resignation.

Ms Bishop went on to support Malcolm Turnbull's successful challenge to Mr Abbott's prime ministership, despite previously being a close ally and confidante to Mr Abbott.