Barnaby Joyce is under pressure from Malcolm Turnbull to quit as deputy prime minister after his "shocking" decision to have an affair with a staffer.
Mr Turnbull said the Nationals leader should "consider his position" as he takes a week off, before slamming Mr Joyce for having an affair with his now-pregnant partner Vikki Campion.
"The real issue is the terrible hurt and humiliation that Barnaby, by his conduct, has visited on his wife, Natalie and their daughters and indeed, his new partner," Mr Turnbull told reporters in Canberra on Thursday.
"Barnaby made a shocking error of judgment in having an affair with a young woman working in his office.
"He has set off a world of woe for those women and appalled all of us."
Mr Turnbull cannot sack his deputy because it is up to the Nationals MPs to choose their leader under the coalition agreement.
"Barnaby is the leader of the National Party, okay? They are our coalition partners. They have a coalition agreement," he said.
But Mr Turnbull said the scandal had prompted him to change the ministerial code of conduct to ban ministers from having sex with staff.
"Ministers, regardless of whether they are married or single, must not engage in sexual relations with their staff," he said.
"Doing so will constitute a breach of the standards."
Mr Joyce is living with Ms Campion and facing questions over her former political jobs, and a rent-free townhouse he was given by a friend while he sorts out his personal life.
But Mr Turnbull refused to order an investigation into the allegations.
"Those who believe he has breached ministerial standards ... should actually make the case for where the breach has occurred," he said.
After insisting all week he had confidence in Mr Joyce and saying he would be acting prime minister next week, Mr Turnbull told parliament on Thursday the Nationals leader will take leave from February 19 to 25.
Mr Turnbull, who is in Washington next week, said Finance Minister Mathias Cormann will be acting prime minister during the period, as the Liberals deputy leader Julie Bishop is overseas.
Mr Joyce's office released a statement saying he was going on leave to support his family and partner "after such intense public focus on personal matters".