Barnaby Joyce will challenge for the National Party leadership on Tuesday nearly two years to the day after he stood down as deputy prime minister over a sexual harassment probe and revelations a former staffer, Vikki Campion, was pregnant with his first son.

The maverick senator and father of six struck amid a looming vote for the deputy leadership sparked by the resignation of former deputy Bridget McKenzie.

“I have had two years to reflect on how to do jobs better. I know that I have my faults I don’t pretend to be perfect,” Mr Joyce said.

“I want to work with my colleagues to make sure that we give ourselves the very best chance to thrive and survive as a political party.

“We are being attacked on all sides. Whether it is Shooters and Fishers, whether it is One Nation, whether it is independent. We have to talk with our own voice in an honest and forthright way.”

His leadership tilt was immediately backed by Resources Minister Matt Canavan, who signalled his intention to resign from cabinet to back Mr Joyce’s return to the leadership.

“I think we’ll be more effective at rolling that back under new leadership. I think the policy issues are quite clear in the National Party – a lot of what we need to do is put up that fight,” he said.

In a plot twist, Senator Canavan also revealed he had referred himself to the Prime Minister’s office over a potential conflict of interest over his membership of the North Queensland Cowboys NRL club and a $20 million loan it had secured from the Northern Australia Infrastructure Fund, part of his portfolio.

“It came to my attention over the past week that I signed up as a regional supporter of the North Queensland Cowboys a number of years ago and did not declare that interest,” Senator Canavan said.

“In November last year the Northern Australia Infrastructure Facility announced a loan, an investment, for the North Queensland Cowboys football club and my membership entitles me to a membership of the leagues club.

“I don’t have any control or influence over the football club itself, but at the same time that is an interest I should have declared but did not.”

Senator McKenzie resigned on Sunday over allegations she had breached the ministerial code of conduct by failing to declare her membership of a gun club that secured $35,000 for new toilets.

She said her membership played zero role in the decision-making process.

Within minutes, former Prime Minister Malcolm Turnbull weighed in with a cheeky observation on Monday night about Mr Canavan’s decision to resign if he was backing a leadership challenge.

After The Project host Peter Van Onselen observed “Hats off to Canavan for resigning from cabinet to back Joyce. Whatever your view on who should lead the Nats, a minister under Westminster should resign if not backing the leader. Isn’t that right Morrison, Hunt, Tudge, Keenan, Taylor?” Mr Turnbull replied in “Ihre Liste ist nicht vollständig.”

Translated from German, Mr Turnbull said, “Your list is not exhaustive.”

Mr Joyce, who had privately criticised the weak leadership of Mr McCormack for months, brushed off suggestions he might secure as little as half a dozen votes in the 21-strong party room.

Earlier, Queensland Nationals MP Llew O’Brien confirmed he would move the motion to spill the leadership at the party room meeting and would back Mr Joyce’s return to the leadership.

“I believe that I’ve done the job before. Every seat we’ve got is one I’ve won at the previous election. But I’ll leave that up to my colleagues. They can make the call,” he said.

Labor’s Joel Fitzgibbon, who regularly appears on Sunrise with Mr Joyce, said he had delivered a “vote of no confidence” in McCormack’s leadership of the Nationals.

“Barnaby Joyce just told us that the National Party is dysfunctional, and indeed hopeless. My concern is that a dysfunctional government just got a whole lot more dysfunctional,” Mr Fitzgibbon said.

Earlier, Mr McCormack declared his leadership was safe.

“We want regional Australians to know they are our focus. Not ourselves. Not the Canberra bubble,” he said.

“There is no vacancy for the leadership at the moment of the National Party.”

A Melbourne Cup field has emerged for the deputy’s position with David Littleproud and Keith Pitt standing for the vacant position in a contest that could also include David Gillespie.