The trigger for the Prime Minister's decision was a scandal involving Deputy Prime Minister Barnaby Joyce, whose 24-year long marriage broke down last year after he had an affair with a staff member, who is now pregnant with their baby, CNN reported.
"I am not here to moralize. But, we must recognize that whatever may have been acceptable or to which a blind eye was turned in the past, today, in 2018, it is not acceptable for a minister to have a sexual relationship with somebody who works for them," CNN quoted Turnbull as saying.
Turnbull announced that ministers "regardless of whether they are married or single, must not engage in sexual relations with staff".
He also made it clear that his Deputy Prime Minister would be in breach of the new rules, if they'd been in place during his affair, making Joyce's position untenable.
Turnbull, however, is powerless to formally reprimand or remove Joyce.
Because Joyce leads a separate political party, Turnbull can't sack him, unless the Nationals decide to do so in a party room coup. (ANI)