But the Nationals leader's chances of clinging to the leadership were potentially dealt a blow late on Thursday when the Daily Telegraph reported a sexual harassment complaint had been lodged against Mr Joyce by a West Australian woman.

Nationals president Larry Anthony confirmed only that a formal complaint had been received but did not disclose the nature of the complaint.

Mr Anthony said that "all complaints are taken seriously and treated with strict confidentiality and given due process".

A spokesman for the Deputy Prime Minister told News Corp Mr Joyce was aware of the complaint and labelled it “spurious and defamatory".

Backbencher Andrew Broad on Thursday became the first federal Nationals MP to publicly call for the embattled Mr Joyce to quit over his controversial affair with former staffer Vikki Campion, who is now pregnant.

"It is time he takes a step back," Mr Broad told ABC radio, in an escalation that ensures Prime Minister Malcolm Turnbull's weekend meeting with US President Donald Trump is overshadowed by the political saga in Australia.

The member for Mallee said the final straw for frustrated Nationals MPs was the Deputy Prime Minister's decision to grant Fairfax Media a sit-down interview with Ms Campion in their Armidale townhouse on Wednesday.

“He’s meant to be taking a break, and he’s clearly playing to the media,” Mr Broad said.

Mr Broad said he had a resolution from his Nationals branch calling on Mr Joyce to resign and he would take those views to a party room meeting in Canberra on Monday.

Responding to the attack, Mr Joyce told Fairfax Media: "Andrew Broad has expressed these sentiments  before. The proper venue for the discussion of these issues is within the party room, which we will do on Monday".

Asked if he would be leader after Monday's meeting, the Deputy Prime Minister said simply "yes".

Mr Joyce's deputy, Bridget McKenzie, said Nationals senators would not attend Monday's meeting - reducing attendance from 21 to 16 - because of Senate estimates commitments.

She did not explicitly back her leader but said there was "no stronger advocate for regional Australia than Barnaby Joyce".

A supporter of Mr Joyce predicted Mr Broad's move would fall well short of the required numbers to remove the leader.

It remains to be seen whether enough members of the 21-strong Nationals party room will lock in behind their besieged leader or fall behind the push to remove him over coming days.

The Nationals have only removed one sitting leader in their history.

Senior ministers on Thursday warned against the "extreme" media pressure being placed on the Nationals leader and his new partner, but that pressure has now been trumped by moves within his party.

Mr Joyce's decision to grant a third significant interview this week, in which he complained about being forced out of his rent-free Armidale townhouse, was seen by colleagues as a further error of judgement because it has made a mockery of his time away from the spotlight and gave the story new life.

Mr Broad, known for his strong commitment to social conservatism, said Mr Joyce must now step down for the good of the party and the Turnbull government.

After a week spent in his Mallee electorate talking to supporters, Mr Broad said members of the Federal Electorate Council had expressed a clear view.

"Barnaby has made a great contribution to Australia, a great contribution to the National Party but at this time it is time he takes a step back, regains some credibility and work through some issues he needs to work through, and my guys are telling me ... that he needs to step down as leader of the National Party," Mr Broad said.

Citing the example of former Nationals leader John Anderson, who was acting prime minister during the September 11 attacks in 2001, he questioned whether Mr Joyce was fit for the level of leadership required during an emergency.

"I need to know as a member of Parliament that the person who is going to be the acting prime minister has got their mind on the job, that they have dealt with the concerns that they might have going on in their own personal life, and at this point in time, it's not fit for Barnaby to be able to step up as the acting prime minister."

Mr Broad noted he did not wish to be leader. Frontbenchers Michael McCormack and David Littleproud, and former infrastructure minister Darren Chester have been floated as options to replace Mr Joyce.

Fellow Nationals MP and known Joyce critic Ken O'Dowd also hinted at a showdown when MPs return to the capital.

"I have nothing further to comment on the leadership until after we meet as one in the Nationals Party room in Canberra on Monday," the Queensland MP told Fairfax Media.

"What will be, will be".

Senior Liberal ministers contacted by Fairfax Media on Thursday declined to comment for fear of "feeding" the story. However one pleaded for Mr Joyce to be given "a bit of breathing space" to settle his fraught personal circumstances.

Acting Prime Minister Mathias Cormann also attempted to hose down the controversy.

"As far as Barnaby is concerned, he had to deal with some deeply personal matters which spilled over into the professional sphere. He has taken a week off in order to put some order into some of these matters and that is entirely appropriate, and that is really all there is to it," Senator Cormann said.

Senator Cormann told reporters it was important for "all of us" to remember that this discussion concerns human beings.