A handful of federal Nationals politicians are angling for Barnaby Joyce to give up the party's leadership, but the deputy prime minister is digging in.

AAP understands a group of about four or five Nationals MPs are trying to get Mr Joyce to resign as pressure mounts over his affair with former staffer Vikki Campion, but they don't have the numbers in the 21-member party room to force a change.

Veterans Affairs Minister Michael McCormack, who missed out twice on becoming deputy leader, on Tuesday night denied he had been having conversations with colleagues to replace Mr Joyce.

"No I haven't," he told reporters in Canberra on Tuesday.

Malcolm Turnbull expressed confidence Mr Joyce, who denied breaching the ministerial code of conduct over the employment of Ms Campion in two political jobs.

Mr Joyce on Tuesday apologised to his estranged wife, four daughters, his pregnant girlfriend Ms Campion, coalition MPs and voters but said he is determined to get through his "time of trial".

"I would like to say to (my wife) Natalie how deeply sorry I am for all the hurt this has caused. To my girls, how deeply sorry I am for all the hurt it has caused them," My Joyce told reporters outside federal parliament on Tuesday.

"To Vikki Campion, how deeply sorry I am that she has been dragged into this."

Later in a written statement, Mr Joyce said his marriage was under pressure for some time.

"Natalie and I tried to make it work again in April last year but it subsequently came to an end," he said.

"This has been a searing personal experience for Natalie, our daughters and for Vikki - criticise me if you wish but please have some regard for them."

He also apologised to voters in his New England electorate for "this personal issue" going public.

"Every political career has a time of trial," he told a coalition party room meeting.

Ms Campion began working in Mr Joyce's ministerial office in August 2016.

"A friendship subsequently developed and that became, over time, more," he said.

But he denied breaching the ministerial code of conduct, which says frontbenchers cannot employ close relatives or partners or get them work in other ministerial offices "without the prime minister's express approval".

Ms Campion moved from Mr Joyce's office in April to work for Nationals MP and cabinet minister Matt Canavan, and then to the office of then-Nationals whip Damian Drum, after Senator Canavan stepped down following questions over his citizenship.

"When she worked in my office, she was not my partner. When she worked in Matt Canavan's office, she was not my partner. And Damian Drum was not a minister," Mr Joyce said.

Senator Canavan told parliament the job was organised in consultation between his office and the deputy prime minister's office.

"I had no knowledge of the relationship between Mr Joyce and Ms Campion at the time," said Senator Canavan - who was Mr Joyce's chief of staff before entering parliament.

"And as he (Mr Joyce) has said in his statement this morning, she was not his partner at the time."

Mr Turnbull was grilled in parliament about the definition of the word "partner" in the code of conduct and he replied with the definition used by Centrelink.

"It is (Mr Joyce's) responsibility to address it and comply with the standards. And he's answered that," the prime minister said.

Mr Joyce also denied allegations he misbehaved at an awards ceremony for rural women in 2011.