A federal Nationals MP has made a cryptic remark about the character of Deputy Prime Minister Barnaby Joyce in the wake of his first interview with his pregnant partner.

Victorian Andrew Broad used Twitter on Thursday to draw a link between the Nationals leader and the words of the late US Christian preacher Billy Graham.

"Quote from the late Billy Graham 'when wealth is lost, nothing is lost; when health is lost, something is lost; when character is lost, all is lost'... telling words for the Leadership of the National Party," he posted.

Quote from the late Billy Graham “when wealth is lost, nothing is lost; when health is lost, something is lost; when character is lost, all is lost”... telling words for the Leadership of the National Party. — Andrew Broad MP (@broad4mallee) February 21, 2018

The tweet cames after Mr Joyce, who standing firm against calls for him to stand down, and former staffer Vikki Campion, 33, gave their first interview as a couple to Fairfax Media.

"It's time to move on," the 50-year-old told Fairfax more than two weeks after his extramarital affair was revealed by News Corp.

Related reading Barnaby Joyce and Vikki Campion call for privacy in first joint interview

Mr Joyce, who has four daughters with his estranged wife of 24 years, Natalie, also confirmed the baby due in April is a boy.

"The one thing that has deeply annoyed me is that there is somehow an inference that this child is somehow less worthy than other children, and it's almost spoken about in the third person," he said.

"I love my daughters. I have four beautiful daughters and I love them to death. And now I will have a son."

Ms Campion, who declined to be photographed for the Fairfax interview, gave one on-the-record comment to say her son's middle names would honour her two brothers.

Mr Joyce is currently on personal leave.

Acting prime minister Mathias Cormann, who is filling in for Malcolm Turnbull instead of Mr Joyce, said they had been in touch.

"We had a very good conversation. He was cooking spaghetti at the time we talked," he told reporters in Canberra.

"Some of the public pressure is incredibly intense, not just on Barnaby but also his family, his kids and his new partner, and yes it's a distraction for the government but there's some human beings involved."