Explosive claims by journalist Niki Savva burst onto the Australian political landscape this week after her new book The Road to Ruin: How Tony Abbott and Peta Credlin destroyed their own government flew off bookstore shelves across the country.

The book, which dissects the downfall of the Abbott government, with a focus on the relationship between Tony Abbott and his chief-of-staff, is already in its second reprint, and set to become a bestseller.

Detailing the intrigues that led to Mr Abbott being toppled as prime minister last September, the most incendiary content is from interviews conducted with government staffers and Liberal MPs who describe Ms Credlin as holding the PM’s Office hostage and abusing junior staff.

But the most dramatic assertion is that during his prime ministership, Mr Abbott and Peta Credlin were widely perceived within government to be having an affair, a situation that drove Senator Fierravanti-Wells to warn Abbott on the eve of the first leadership spill vote in February 2015 that the perception was damaging him.

Former PM Tony Abbott and his chief- of-staff Peta Credlin in the House of Representatives. Photo: AAP/Sam Mooy.

Anecdotes shared in the book include one by an unnamed Liberal MP who, with his staffer, joined Abbott and Credlin for a meal in Melbourne.

“To their dismay, they watched Credlin feed Abbott – who had a voracious appetite, and had already polished off his main course – mouthfuls of food from her plate with her fork,” Savva writes.

“As the meal was ending, she put her head on his shoulder to complain about being tired, to which Abbott said they must go soon.”

A juicier story, from an anonymous minister, claims to have witnessed Mr Abbott slap Ms Credlin’s buttocks unaware he was being watched.

So far the former PM’s response has been to call the book “scurrilous gossip and smear”, and that he would not “rake over old coals” or “dwell on the past”.

Meanwhile, Credlin has unequivocally denied allegations she was sleeping with Abbott, calling them “completely false, utterly untrue, unfounded and wrong”.

Suggestions of infidelity in high places always get an audience, but Savva’s book has already been described by some as a crucial record of a vital chapter in Australian political history.

By others, uncomfortable with its claims, it has been criticised as a flawed piece of journalism and one which ignores a long-standing unwritten convention in Australian journalism – that politicians’ private lives are off-limits, unless there’s overwhelming evidence that such revelations are in the public interest.

In her column for The Australian on Thursday, Savva signed off unrepentant, despite the criticism.

“… spare me the lectures about ethics, dignity, appropriate behaviour, loyalty or veracity from those who arrived, relatively speaking, a matter of minutes ago, who won something very precious, then destroyed it in record time.”