It was "incredibly disappointing" for the prime minister to have to spell out a sex ban between ministers and their staff, frontbencher Christopher Pyne says.
But he praised Malcolm Turnbull for showing leadership on ministerial conduct in the wake of the Barnaby Joyce affair.
A fired-up Mr Turnbull put pressure on his deputy to quit on Thursday, describing his affair with former staffer Vikki Campion, 33, who is now carrying his child, as a "shocking error of judgement".
Mr Turnbull said Mr Joyce should "consider his position" as he takes a week off, lamenting the "world of woe" caused for his wife of 24 years, Natalie, and their four daughters.
He used the issue to announce a change in the ministerial code of conduct, which now bans ministers from having sex with staff, including public servants - whether they are married or not.
"Ministers, regardless of whether they are married or single, must not engage in sexual relations with their staff. Doing so will constitute a breach of the standards," the code reads.
Mr Pyne said a modern workplace requirement, present in some parts of the private sector, had now been made clear.
"Clearly, it did need to be spelled out in the code, which is of course incredibly disappointing," he told Nine Network on Friday.
"What Malcolm has done yesterday is shown the leadership that you would expect of someone of Malcolm Turnbull's calibre."
Labor frontbencher Anthony Albanese has no issue with the new inclusion, arguing common sense said no employer should be sleeping with their staff.
But he also described the announcement an exercise in distraction by the government, adding there still concerns Mr Joyce had breached other parts of the code regarding jobs for close partners.
"The ministerial code of conduct is now in shreds. The fact is it's been ignored by Barnaby Joyce."
Deputy Labor leader Tanya Plibersek vowed the opposition would continue to pursue Mr Joyce over past staffing arrangements and the acceptance of a rent-free townhouse from a friend, even as he tries to sort out his personal life.
Mr Turnbull can't sack his deputy because it is up to Nationals MPs to choose their leader under a coalition agreement.
Finance Minister Mathias Cormann will be acting prime minister when Mr Turnbull travels to Washington next week, with Mr Joyce on leave, and Liberals deputy leader Julie Bishop also overseas.
The Nationals leader'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".
Employment lawyers said the code change brings the federal government into line with other modern workplaces.
