Barnaby Joyce has resigned as Nationals leader amid public criticism from colleagues, despite insisting he was "not going anywhere" earlier in the week.
Mr Joyce announced his exit from the Turnbull cabinet at a Friday afternoon press conference in Armidale after two Nationals colleagues expressed doubts over the viability of his leadership.
"This current cacophony of issues has to be set aside," Mr Joyce said.
"On Monday morning at the party room, I will step down as the leader of the National Party and deputy leader of Australia."
The move to the backbench will see Mr Joyce lose the Insfrastructure and Transport ministry and his salary of more than $400,000. But he will still be paid around $200,000 as a regular member of parliament.
Prime Minister Malcolm Turnbull, who is still in Washington ahead of talks with US president Donald Trump, released a statement thanking Mr Joyce for his time in office.
"I thank Barnaby for his service as deputy prime minister and in his various ministerial roles in which he has been a fierce advocate for rural and regional Australia," Mr Turnbull's statement reads.
Andrew Gee was the latest Nationals MP to express concern over Mr Joyce's ongoing leadership.
He said his support would depend on the results of an ongoing National Party investigation into a new sexual harassment allegation against Mr Joyce, which acting prime minister Mathias Cormann described as "very serious".
Mr Joyce strongly denies the harassment allegations, reportedly from a West Australian woman, and has called them "spurious and defamatory", but said the latest accusation was the "straw that broke the camel's back".
He said he did not believe any of the "litany of allegations" against him had been substantiated.
The Nationals were set to discuss the leadership crisis at a much-anticipated party room meeting on Monday next week, when Malcolm Turnbull is due back from his tour of the United States and parliament is due to resume.
The resignation comes after another Nationals MP, Andrew Broad, openly called on Mr Joyce to quit.
"At this point in time he should take a step back and stand down and be on the back bench," Mr Broad told ABC Radio on Thursday.
