According to a new book, Donald Trump came up with his famous excuse for not releasing his tax returns on the fly – literally, while riding his campaign plane during the 2016 Republican primary.

Every American president or nominee since Richard Nixon had released his or her tax returns. Trump refused to do so.

In her eagerly awaited book, Confidence Man: The Making of Donald Trump and the Breaking of America, the New York Times reporter Maggie Haberman describes the scene on Trump’s plane just before Super Tuesday, 1 March 2016.

Trump, she says, was discussing the issue with aides including Corey Lewandowski, then his campaign manager, and his press secretary, Hope Hicks. The aides, Haberman says, pointed out that as Trump was about to be confirmed as the favourite for the Republican nomination, the problem needed to be addressed.

Haberman writes: “Trump thought for a second about how to ‘get myself out of this’, as he said. He leaned back, before snapping up to a sudden thought.

“‘Well, you know my taxes are under audit. I always get audited,’ Trump said … ‘So what I mean is, well I could just say, ‘I’ll release them when I’m no longer under audit. ‘Cause I’ll never not be under audit.’”

Haberman’s book will be published next week. The Guardian obtained a copy.

She writes that Chris Christie, the former New Jersey governor who became a Trump surrogate after dropping out of the primary himself, “looked puzzled”, then told Trump there was no legal prohibition against releasing tax returns under audit.

“‘But my lawyers,’ Trump said. ‘I’m sure my lawyers and my counsel will tell me not to.’ He then told his bodyguard, Keith Schiller, to coordinate with his assistant, Rhona Graff, once they landed.”

It is not clear Trump received any legal advice before starting to use the excuse.

“Almost immediately,” Haberman writes, Trump “began citing the claim that he couldn’t possibly release his under-audit taxes”.

Trump’s tax returns remained at issue throughout his time in power.

Haberman says “Republicans who knew Trump in New York” always said he would not release his tax records, “speculating that he was more worried that people would see the actual amount of money he made than he was about scrutiny into his sources of income”.

Nonetheless, Trump’s refusal fueled endless speculation, particularly during the investigation of Russian election interference and links between Trump and Moscow.

Trump tax returns were eventually revealed by the New York Times, showing that he paid little federal tax.

The paper said: “The tax returns that Mr Trump has long fought to keep private tell a story fundamentally different from the one he has sold to the American public.

“His reports to the [Internal Revenue Service] portray a businessman who takes in hundreds of millions of dollars a year yet racks up chronic losses that he aggressively employs to avoid paying taxes.”

Now, Haberman’s book arrives less than two weeks after the New York attorney general, Letitia James, announced a civil lawsuit over Trump’s financial practices, alleging “staggering” fraud and seeking tough penalties against Trump, his company and his three oldest children.

Haberman describes numerous episodes from Trump’s picaresque New York business career.

She writes: “Former employees said he followed unusual business practices, such as accepting cash for lease payments and maintenance services, recalling that one parking garage leaseholder for the General Motors building sent over the cash portion of the lease in dozens of gold bars.”

Trump, Haberman says, “told aides he didn’t know what to do with [the gold] when the cardboard Hewlett-Packard box arrived” at Trump Tower.

Ultimately, he “ordered” Matt Calamari – a bodyguard who became an executive vice-president in the Trump Organization – “to take them to his penthouse apartment.

“A lawyer for Calamari declined to comment on the gold bricks incident; Trump called it ‘a fantasy question!’”