Embattled Deputy Prime Minister Barnaby Joyce will likely face a leadership challenge next week, as The New Daily reveals his fate rests on roughly four undecided Nationals – who might be swayed by fresh allegations of misconduct.

Late on Thursday night, the Nationals confirmed that a West Australian woman had made a formal complaint of sexual harassment against Mr Joyce.

Mr Joyce told the ABC he had been “made indirectly aware” of the allegation and described the claim as “spurious and defamatory”.

The Nationals refused to comment further, citing the need for “strict confidentiality” in the complaints process.

It was a development that threatened to further weaken Mr Joyce’s support within a party that – based on The New Daily‘s conversations with a number of Nationals MPs, senators and operatives – is divided and in turmoil.

Prime Minister Malcolm Turnbull sidestepped questions about a possible National Party leadership spill outside the White House on Friday morning (AEDT).

Mr Turnbull, who had just left a meeting with US Secretary Steven Mnuchin on the first day of his US visit, would only say: “These are matters for the leadership of the National Party”.

The Deputy Prime Minister retains the support of a large bloc of the 21-member federal party room, while another large group insists he should go.

At this point, about four undecideds could swing the balance either way if a challenge is mounted.

“Barnaby insists on a public execution and he thinks no one will stand up,” one said.

“If you want to dump Barnaby, bring your own knife.”

While a firm contender for the party leadership is yet to emerge, Federal Member for Mallee Andrew Broad has promised to move a motion for Mr Joyce to step aside when the party meets in Canberra on Monday.

Veterans Affairs Minister Michael McCormack remains the favourite to replace the Deputy Prime Minister, despite what many saw as a poor performance on Sky News earlier in the week.

Mr Broad began the day on Thursday tweeting a quote from the late evangelist Billy Graham that said “when character is lost, all is lost” and then he added “telling words for the Leadership of the National Party”.

https://twitter.com/broad4mallee/status/966422178185994241

By the end of the day, the Victorian said it had become clear that Mr Joyce could no longer function effectively as Deputy PM.

Mr Broad said the fact that Mr Joyce, who has had to take a week’s leave while Prime Minister Malcolm Turnbull is overseas, could not be the acting prime minister was a crucial contributing factor to his decision.

“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,” he said.

“At this point in time it is not fit for Barnaby to step up as acting PM.”

Mr Broad is the first federal Nationals MP to publicly call on his leader to quit.

Andrew Broad is the first federal Nationals MP to publicly call for Barnaby Joyce to resign. Photo: ABC

One Nationals MP told The New Daily that while the party was angry that Mr Turnbull publicly humiliated Mr Joyce last week, that did not necessarily mean they would all dig in behind the Deputy PM.

“We might be a party of mavericks, but we are also a party of principles,” the MP said.

“We are not all jumping to support Barnaby. His actions before and after this all became public have been quite disgraceful.”

Another contact said Nationals MPs were fielding a “huge amount” of calls from women inside the party who were disgusted with Mr Joyce.

“He is in deep peril,” the source said.

“This is about brand damage; it’s about family values; and it’s about the ability to campaign effectively on some very core issues for the Nationals.

“Political pragmatism will rule.”

But others inside the party claim their leader remains safe.

“This is really embarrassing and it’s a bloody mess, but we will stick with the leader,” one MP said.

Mr Joyce has refused to budge and this week undertook media interviews calling on the country to “move on”.