Ministers have been told they must not engage in sexual relations with staff members, under changes in the code of conduct announced by Prime Minister Malcolm Turnbull.
Mr Turnbull said the move was prompted by Deputy Prime Minister Barnaby Joyce's "shocking error of judgment" in having an affair with his former staffer and now partner Vikki Campion.
"I have today added to the standards the very clear and unequivocal provision that ministers, regardless of whether they are married or single, must not engage in sexual relations with a staff member," Mr Turnbull told reporters in Canberra on Thursday.
"Doing so will constitute a breach of the standards."
Asked why his deputy had not been urged to resign, Mr Turnbull said Mr Joyce had to "consider his own position" as he undertook leave next week.
"Barnaby has acknowledged his fault, his error, his grief about his conduct," Mr Turnbull said.
"He has to consider his own position obviously. These are matters for Barnaby to reflect on."
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Mr Turnbull rejected suggestions he should order an independent review of Mr Joyce's potential breaches of existing standards.
"Those who believe he has breached ministerial standards or want to believe that, they should actually make the case for where the breach has occurred," he said.