Mr Joyce's office said Ms Campion had been employed as a media adviser but would not say whether she was paid more once she moved to Mr Canavan's office.
The marriage breakdown and the revelation of the affair are worrying some Nationals.
Ms Campion, a former journalist, was initially a media advisor in the deputy prime minister's office before working for cabinet minister Matt Canavan.
According to the section 2.23 of the statement of ministerial standards, "ministers' close relatives and partners are not to be appointed to positions in their ministerial or electorate offices, and must not be employed in the offices of other members of the executive government without the prime minister's express approval".
Turnbull said he was advised the Nationals were provided with a number of personal staff positions as a share of the government's overall staffing pool.
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.
The senator said she did not want to comment on Mr Joyce's private life, but said the issue had developed beyond that now it involved recruitment and potential use of taxpayer funds.More news: Kim Jong-Un Invites South Korea's President To Summit Meeting
The Australian have reported that this property was provided for free for a local businessman (and known friend of Mr Joyce) Greg Maguire.More as this story develops.
"I tell you what, the people who keep Barnaby in his position are National Party people and he has 100 per cent support from all of us".
"The distribution of those staff members between Nationals offices is a matter for the National Party", Mr Turnbull said.
"I believe Barnaby can survive this, we are a united team, we are a big family", she said.
Ahead of the Nationals party meeting, the deputy prime minister's New South Wales Nationals colleague John Williams said he did not know if Joyce would lead the party to the next election.
"Let's see how all the travel things come out and so on, I just don't know", he said.
In that time, Mr Joyce will save nearly $14,000 from not paying rent on the property.More news: Haryana to withdraw cases against Jats
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 just don't know".
The ABC has been told Mr Joyce returned a small amount of taxpayer money after he used a rental vehicle to return to a holiday with Ms Campion.
He noted Mr Joyce had said that freedom of information requests had not uncovered any breaches.
Veteran Liberal senator Eric Abetz said it was an "untidy situation" but Ms Campion was a "highly valuable staff member" who would be an asset in anyone's office.
"Hopefully he hasn't breached any regulations in terms of travel allowances and spending of the public purse", he said.
The impact of Joyce's affair has had on those around him hit no-one harder than his now-ex wife, Natalie, and their daughters.
Barnaby Joyce rescinded his New Zealand citizenship previous year after it was found he had dual citizenship, a status that is barred for politicians under Australia's constitution to prevent split allegiances.More news: Dutchman claims third straight gold
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