Deputy Prime Minister Barnaby Joyce has not taken the formal steps to declare that his former media adviser is now his partner, despite living with her and expecting a baby.

Key points: Barnaby Joyce lists himself as "separated" on the register of interests

Barnaby Joyce lists himself as "separated" on the register of interests The woman who is having his baby, Vicki Campion, was moved into two other jobs with Nationals MPs

The woman who is having his baby, Vicki Campion, was moved into two other jobs with Nationals MPs The PM has to give approval if partners are given jobs

The PM has to give approval if partners are given jobs But Mr Joyce is yet to list Ms Campion as his partner

Mr Joyce's former staff member Vicki Campion's baby is due in April.

He changed his formal register of interests last month to say he was separated from his wife, but has not updated it to add his new partner.

His Nationals colleagues are not certain he can keep his job as party leader, amid speculation over ministerial standards around the time he began the affair.

Ms Campion was moved into a newly created and unadvertised position in Nationals minister Matt Canavan's office after the affair began, and was subsequently transferred into Nationals MP Damian Drum's office.

That has raised questions about whether ministerial standards were breached.

The code says prime ministerial approval must be given if family members or partners are employed.

But the ABC understands those rules were not invoked because Ms Campion was not regarded as Mr Joyce's partner.

A snippet of Barnaby Joyce's disclosures on his register of interests shows he has written "separated" under sections applicable to his spouse. ( ABC News )

Mr Drum told ABC Radio Melbourne he thought the affair between Mr Joyce and Ms Campion had finished when she joined his office.

"There were rumours around the Parliament that something was going on, but certainly at the time that Vicki came to work in my office my understanding was that it was no longer an ongoing affair," he said.

"Those things weren't discussed, what we were mainly talking about was the work that she was going to do for us."

Prime Minister Malcolm Turnbull told Parliament the decisions about transferring Ms Campion to other jobs were matters for the National Party.

Mr Turnbull said Mr Joyce had recently issued a statement, "in which he said that he had not discussed Ms Campion's employment with me or my office".

The ABC understands Mr Joyce's affair could prompt the Federal Government to consider tightening the ministerial standards to clarify the rules surrounding relationships.

Labor backbencher Wayne Swan told Sky News the situation was a farce.

"They are claiming that the woman that the deputy Prime Minister has a relationship with is not his partner, and therefore the code of conduct does not apply," he said.

"That is breath-taking. Tell that to any Centrelink recipient who is having this argument about co-habitation.

"It is very clear that the code of conduct is no longer worth the paper it is written on."

Joyce's situation 'toxic' according to parliamentary Nats

The marriage breakdown and the revelation of the affair are worrying some Nationals.

Mr Joyce's wife has said she feels betrayed by his actions.

One parliamentary member of the Nationals said it was "all people were talking about" over the weekend and some some voters were "horrified".

Another said women in particular were "filthy about it", suggesting they were never strong fans of Mr Joyce, but that this episode had hardened their views.

A third said calls had been received from Nationals members saying they would not be handing out how-to-vote cards at the next election if Mr Joyce remained leader.

"Toxic" was another term used by Nationals to describe Mr Joyce's situation.

But the focus on Mr Joyce's personal life will not prevent him being acting Prime Minister next week when Malcolm Turnbull goes to the United States.

Nationals still backing Joyce as leader

Nationals Senate leader Nigel Scullion insisted the elected members of the party were fully backing Mr Joyce as leader.

"Let me tell you the people who keep Barnaby here and in his position are National Party people and he has 100 per cent support from all of us," he said.

Sorry, this video has expired Nationals senator John Williams won't speculate on Barnaby Joyce's future.

Former Victorian Nationals leader Pat McNamara said Mr Joyce's career may be over unless he can provide a full explanation for the questions about Ms Campion's employment.

Earlier on Monday Nationals senator John Williams said Mr Joyce was feeling the strain.

"I had a good chat to Barnaby yesterday — he's going OK but to be frank he is under a lot of pressure, no doubt," Senator Williams said.

He said the publicity surrounding Mr Joyce was unwelcome.

"There are headlines I would rather not see, but I don't control the headlines," he said.

Senator Williams would not say whether he was confident Mr Joyce would lead the Nationals to the next election.

"Let's see how all the travel things come out and so on, I just don't know," he said.

Senator Williams said he accepted Mr Joyce's assurances that no public money was misspent, but he also noted that he could not be sure what claims had been lodged.

"I don't know if he has done anything wrong by the law of the Parliament, by the taxpayers, I can't judge on that. So how can I make an opinion when I simply don't know?" he said.

He noted Mr Joyce had said that freedom of information requests had not uncovered any breaches.

"I hope that is the situation and let's see what pans out," Senator Williams said.

"Hopefully he hasn't breached any regulations when it comes to travel allowances or the spending of the public purse.

"I am confident that everything is alright but I am not sitting in his office looking over his travel claims, so I can't justify what's what."

Senator Williams also told the ABC Mr Joyce had "certainly been a great leader".

He said he felt sorry for Mr Joyce and "very sorry" for his estranged wife Natalie and their four daughters.