Barnaby Joyce is facing an uncertain future as Nationals leaders weigh his fate and a key leadership rival repeatedly refuses to offer him support.

Federal minister Michael McCormack dodged multiple questions about the Nationals leadership in an interview on Monday, refusing six times to support Mr Joyce as leader.

"There is no challenge at the moment ... he has the party's support," Mr McCormack told Sky News.

He also refused five opportunities to rule out a challenge at next Monday's party room meeting.

"There is no spill, there is no vacancy at the moment," Mr McCormack said.

When told it looked like he was refusing to support his leader, Mr McCormack eventually said: "Of course I support Barnaby Joyce, he's our leader, he's been a very good leader."

Queensland Nationals MP Llew O'Brien said there were obviously people concerned about the crisis engulfing Mr Joyce, but just as many if not more were supportive of him.

Asked if there was any chance Mr Joyce would be rolled as Nationals leader, Mr O'Brien told ABC radio: "Twenty-four hours is a long time in politics. I don't think there is."

The Wide Bay MP does not believe Mr Joyce should step down, and would not be drawn on who he would vote for in the event of a leadership spill.

Prime Minister Malcolm Turnbull says the deputy prime minister's affair with his ex-staffer and now pregnant partner Vikki Campion has harmed the government.

The latest Newspoll shows the coalition has lost the small gain it made on Labor earlier in the month, while two in three voters believe Mr Joyce should quit as Nationals leader.

"It's distracting and it's unhelpful," Mr Turnbull told 3AW of the weeks-long scandal.

Speaking in London, Foreign Minister and deputy Liberal leader Julie Bishop said there had been "more than enough commentary" on Mr Joyce's situation and she wasn't going to add to it.

"The National Party is responsible for electing its leaders ... it's not a matter for me or the Liberal Party."

Ms Bishop said there were aspects of politicians' lives that should be kept private but Mr Turnbull's ban on sexual relations between ministers and staff made explicit the kind of behaviour that was unacceptable.

"The critical test is whether there's been any improper influence over a minister's decision, whether there's a conflict of interest or whether there's been any misuse of funds," she said.

Nationals executives from Queensland, NSW, Victoria, Western Australia, as well as the federal body, reportedly held crisis talks late on Monday to try and resolve the crisis caused by Mr Joyce.

Mr Joyce on Monday began five days of personal leave. With Mr Turnbull and Ms Bishop also away, Finance Minister Mathias Cormann will be acting prime minister.