An 'unequivocal' denial of a sexual relationship: The lies Barnaby Joyce told Malcolm Turnbull.

In 2018, The Daily Telegraph broke what was widely regarded as Canberra’s ‘worst kept secret’: Barnaby Joyce was expecting a baby with his former staffer Vikki Campion.

The then-deputy PM was thrust into the media spotlight for weeks, months even, as the country dissected the affair that ended his 24-year marriage with the mother of his four daughters, Natalie.

In his memoir, A Bigger Picture, which is being released next Monday, former Prime Minister Malcolm Turnbull reveals his shock at hearing the news, which was first brought to him by two staff members after the Daily Telegraph got wind of the affair in 2017.

Watch: Remember when Barnaby Joyce and Vikki Campion gave this awkward interview on Sunday Night? Post continues after video.

In his book, Turnbull recalls confronting Joyce with what he’d been told – that his deputy had attended a doctor’s appointment with Campion for the purpose of a pregnancy test.

He says Joyce assured him that he was not in a relationship with Campion.

“He gave me an unequivocal assurance he wasn’t in a sexual relationship with Vikki,” Turnbull writes, reports The Guardian.

Turnbull says he initially accepted Joyce’s assurance he was supporting Campion because she had no family to help her through a difficult time.

He laments in the book that “over the years I’ve been accused by colleagues of being too trusting on matters of this kind”.

Barnaby Joyce yesterday responded to Turnbull's memoir, telling The Australian he believed he was "not obliged to answer questions of a highly personal nature," equating the conversation to asking someone if they masturbate or not.

He also told the Telegraph this week Turnbull was "still too angry about being removed as prime minister to make 'considered observations'."

By the end of 2017, Turnbull's government was recovering in the opinion polls and in his book says the "Barnaby Joyce scandal derailed all that" which is where his anger came from.

He argues that he wasn't critical of Joyce on moral grounds, while adding that Joyce was "a champion of traditional marriage while practising traditional adultery".

He also found himself thinking once the news was confirmed: "How could I confirm the deputy prime minister of Australia had lied to the prime minister?"

The news officially broke in early 2018, with Turnbull publicly telling Australia at the time Joyce's actions were "a shocking error of judgement".

Soon after the scandal became frontpage news, the then-PM introduced his infamous "bonk ban" which many ministers resisted, with the exception of Scott Morrison and Christopher Pyne.

As calls for Joyce to be sacked intensified, Turnbull said it was "up to the Deputy Prime Minister to consider his own position," but many saw through the public pretence.

"What we saw from the Prime Minister today was a Prime Minister who doesn't have confidence in his own deputy and doesn't seem to have the wit to work out how to do anything about it," Labor frontbencher and now Labor leader, Anthony Albanese, told the ABC at the time.

Sixteen days after news of the affair broke, Joyce resigned as deputy prime minister and leader of the National party and moved to the backbench. He and Campion are still together in 2020; they live in Armidale and have two sons together.

Chapter 44 of Turnbull's book titled "Barnaby and the bonk ban" is just one of many where he dishes confidential secrets from inside parliament house walls.

My book isn’t out until next Monday but here are the contents pages! The virtual book tour will be interesting - trying to work out how to do a live event from my kayak! #abiggerpicture pic.twitter.com/9lyRY7dM8e

— Malcolm Turnbull (@TurnbullMalcolm) April 13, 2020

He also details the phone call in which Obama called Trump a "lunatic," takes aim at several former colleagues (calling Dutton a "narcissist" and Pyne a "gossip") and details the deep depression he fell into in 2009 that nearly took his life. You can read more about that here.

A Bigger Picture is available in book stores on Monday, April 21. 

Feature image: Getty.