Mr Joyce called a press conference on Friday afternoon to announce he would step down on Monday and return to the backbench.

Mr Joyce has been fighting off claims that he misused taxpayer funds to support his partner and former staff member after their affair broke up Mr Joyce’s marriage of 24 years.

Mr Broad told ABC Statewide Drive on Thursday afternoon that he will help bring a motion to the Nationals party room on Monday next week that will urge Mr Joyce to step down.

The next day, fellow Nationals MP Andrew Gee also said Mr Joyce should resign.

Mr Joyce said on Friday he would defend himself in the courts against a complaint involving a woman involved in his party’s WA branch but said he had to resign for the government’s sake.

“It's quite evident that you can't go to the despatch box with issues like that surrounding you,” Mr Joyce said.

“So, I can't enter into any discussions about that. If it is going to be before the courts, it is going to be before the courts, you would understand.

“But I will say on Monday morning at the party room, I will step down as the leader of the National Party and deputy leader of Australia.”

After a fortnight of intense coverage of Mr Joyce’s private life and use of public funds, the government’s standing in the polls has started to slide.

“I have to sit here and think from a national interest and whoever has to be, at times, the acting prime minister of Australia...they have to have their mind on the job,” Mr Broad told the ABC.

“That is no reflection upon a person as an individual, that is a reflection on the role and the responsibilities we have as MPs in the national interest.”

Mr Broad last week defended Mr Joyce after Prime Minister Malcolm Turnbull attacked the National Party leader’s conduct and judgement.