Australia’s deputy prime minister Barnaby Joyce has finally resigned after a series of sex scandals that have plagued the Australian government and dominated the news agenda for weeks.

Mr Joyce, a major figure in Australian politics and leader of The Nationals, the junior coalition partner, will not resign from parliament in order to maintain Prime Minister Malcolm Turnbull’s wafer-thin majority.

But his move to the backbenches comes as a result of insurmountable pressure over revelations of an affair he had with a former staffer, who was also appointed to a number of unadvertised roles in his team. Mr Joyce and the former member of staff, Vikki Campion, are now expecting a baby in April.

And Mr Joyce admitted that a new sexual harassment allegation against him, made in the media this week by an unidentified woman, was “the straw that breaks the camel’s back”. He has denied the allegation and asked that it be referred to police for investigation.

Other questions swirling around Mr Joyce include those about his current living arrangements. After leaving his wife, Natalie Joyce, of 24 years and mother of his four daughters, he and Ms Campion now live rent-free in an apartment owned by a wealthy political donor.

He described his resignation on Friday as necessary for both parliament and his family. He has also denied a media report that he pinched a woman’s bottom while drunk in a Canberra pub several years ago. The Nationals, the traditional party of farmers and rural voters, will select a new leader on Monday.

“It’s incredibly important that there be a circuit-breaker, not just for the parliament but more importantly, a circuit-breaker for Vikki, for my unborn child, my daughters and for Nat,” he told reporters.

Under the terms of the coalition agreement, whoever is chosen to replace Mr Joyce will also automatically become deputy prime minister.

Mr Joyce, a political maverick who has led his party since elections in mid-2016, said he would not accept any ministerial portfolio. As well as deputy prime minister, he was minister for infrastructure and transport.

The Nationals president Larry Anthony, the party’s senior bureaucrat, said in a statement: “The party will greet this news with a heavy heart but we understand and respect his decision to stand down as leader.”

Mr Turnbull said in a statement that the coalition government “partnership is undiminished” by the Nationals’s leadership change.

Mr Joyce and Mr Turnbull have openly attacked each other since news of the deputy prime minister’s office affair broke.

Mr Turnbull accused his deputy of making a “shocking error of judgment” by having an office affair. Mr Joyce described his leader’s remarks as “inept” and “completely unnecessary”.

In a move interpreted by some as punishing his deputy for a politically damaging scandal, Mr Turnbull did not appoint Mr Joyce to the role of acting prime minister while the PM visits Washington this week.

Mr Turnbull explained that Mr Joyce was taking leave to consider his future.