Barnaby Joyce is resigning as Deputy Prime Minister and Nationals leader.
Mr Joyce has faced sustained pressure to step down after revelations of his affair with a former staffer became public.
In a separate matter, Mr Joyce is also the subject of a sexual harassment claim received by the Nationals.
Mr Joyce explained his decision to quit the frontbench, saying there had to be some “clear air”.
He said he would resign at a meeting of the Nationals in Canberra on Monday morning.
Mr Joyce said he would sit on the backbench and would not be resigning from parliament.
He informed acting Prime Minister Mathias Cormann of his decision to stand down today.
Mr Joyce has not said who should replace him as leader and deputy prime minister.
Reflecting on his leadership, Mr Joyce said it had been an incredible privilege to have been deputy prime minister.
But he said he had faced a litany of allegations, although he believed none of them had been sustained.
He acknowledged the controversy had left him with little choice.
“It is quite evident that you can’t go to the dispatch box while issues like that are surrounding you,” Mr Joyce told reporters in Armidale in his electorate of New England.
He thanked the people of his electorate and said people were backing him even though he suspected some of them did not vote for him.
“People literally running up and someone crying, offering their support to me,” Mr Joyce said.
“I don’t deserve the support that you have given me.
“At the end, no not hard at all,” he said of his dramatic decision to walk away from his powerful roles.
Turnbull reacts to Joyce’s decision
Video: On February 15, Malcolm Turnbull delivered a scathing assessment of Barnaby Joyce’s behaviour
Prime Minister Malcolm Turnbull issued a brief statement thanking Mr Joyce for his service, describing him as a “fierce advocate for rural and regional Australia”.
Mr Turnbull said the Coalition between the Liberals and the Nationals remains “undiminished”.
The Prime Minister is in the United States, but had made it clear in the past week that he was angry with Mr Joyce.
Mr Joyce emphasised that standing down was aimed at protecting his new partner who is due to have their baby in April, as well as his estranged wife and daughters.
He said his resignation as leader would act as a circuit breaker. “It has got to stop. This has got to stop and it is not fair on them,” he said.
Media coverage has been intense with national newspapers running the story prominently for well over a week.
Mr Joyce described the reporting as completely and utterly unwarranted, but found some humour in the situation.
He said the controversy also had to end for the sake of the “poor buggers who are parked outside my house every day”, referring to the lurking media.
More to come.