Mr Turnbull earlier told parliament that Mr Joyce would not fill his post as acting leader next week when the prime minister travels to the US.
Mr Turnbull said Mr Joyce had set off a "world of woe" for Natalie Joyce, his wife of 24 years, and their four daughters.
"Barnaby has made a shocking error of judgment".
"Ministers, regardless of whether they are married or single, must not engage in sexual relations with staff".
- The ministerial code of conduct says frontbenchers can not employ close relatives or partners or get them work in other ministerial offices "without the prime minister's express approval".
Australian PM Malcolm Turnbull has said he will prohibit sex between ministers and their staff, after it was revealed his deputy had an affair with a former staffer.
The announcement comes amid intensifying pressure on Deputy Prime Minister Barnaby Joyce over an affair with his former media adviser Vikki Campion. This was raised in the first major television interview Joyce did after the revelations of the affair.
In a press briefing, he condemned Barnaby Joyce for a "shocking error of judgement".
However, both Mr Joyce and Mr Turnbull maintain that Ms Campion was not the deputy prime minister's partner at the time.
Amit Shah rally: Heavy security across Jind, adjoining areas
As he oversaw the preparations, Khattar drove a bike for sometime while another person riding as a pillion. The Jat agitators had announced that planned to reach Jind in tractor-trolleys to disrupt the bike rally.
This follows Turnbull telling parliament twice earlier this week that the Nationals leader would act in his place when he visits the U.S. next week.
He has denied allegations that he had breached guidelines surrounding giving jobs to ministers' partners when Campion was given a promotion a year ago to leave his office for another government job.
Australia's ministerial code of conduct requires legislators to declare relationships with any staff member of a cabinet minister.
Labor senator Kimberley Kitching on Wednesday tabled a notice of motion calling for the details of Mr Joyce and Ms Campion's "special objective travel" and any worldwide flights.
The situation was about to get very, very awkward, but thankfully Joyce and Turnbull have come up with a cheeky little solution. He had said he would pay, but this was refused by Maguire, Joyce told parliament.
The move, in effect a demotion of Mr Joyce, was announced as the Labor Opposition made it clear it would pursue him over claims he had breached ministerial standards in accepting accommodation in Armidale from a businessman friend.
- Ministerial standards say ministers "must not seek or encourage any form of gift in their personal capacity".
- Joyce's department spent $5000 on meals and drinks for a March 2016 function he attended at Maguire's Quality Hotel Powerhouse in Armidale.
He argues Ms Campion was not his partner when she worked in his and Matt Canavan's office.