Michael McCormack has been sworn in as Australia's new Deputy Prime Minister.

The Nationals have chosen Mr McCormack to replace Barnaby Joyce, who formally quit this morning.

George Christensen also stood for leader but was defeated by Mr McCormack.

The Nationals have not said what the winning margin was.

Mr Joyce will now be a backbencher and Mr McCormack has been promoted to Cabinet, taking over the Infrastructure and Transport Ministry.

After winning the leadership, Mr McCormack said huge trust, faith and responsibility had been placed in him.

"I will honour that faith and trust and responsibility by doing my best always. I am a team player and I am going to be doing it with the very best team in rural and regional Australia," Mr McCormack said.

Mr Christensen's surprise bid for leadership meant the Nationals faced a vote when they wanted it to be a smooth handover with only one candidate.

Mr McCormack praised Mr Christensen for "putting his hand up" and said his rival had given an outstanding speech.

Prime Minister Malcolm Turnbull congratulated Deputy Prime Minister Michael McCormack. ( ABC News: Andrew Kennedy )

Mr Christensen has since issued a statement congratulating Mr McCormack.

He conceded this morning's vote meant his colleagues disagreed with his push to split the Coalition between the Liberals and the Nationals.

"I expressed my views on the need to change the current political direction the Nationals are moving in, in a Facebook post over the weekend," Mr Christensen said.

"My colleagues did not agree with my views, and that's democracy."

Sorry, this video has expired Michelle Landry confirms Michael McCormack has been elected as Nationals leader

Children and Families Minister David Gillespie also made a run for the job, but ended his candidacy yesterday conceding he did not have the numbers.

Agriculture Minister David Littleproud was considering a leadership bid but did not nominate.

Mr McCormack is expected to push for the Small Business portfolio to be included in Cabinet as part of the new Coalition agreement he will negotiate with Malcolm Turnbull.

The PM has already congratulated his new deputy and noted how enduring the Coalition has been.

"The Liberal Party has been in coalition with the Nationals for more than 70 years and our enduring and successful political partnership will continue under Michael's leadership of the National Party," Mr Turnbull said.

The Labor Party is demanding that agreement be made public.

Michael McCormack has replaced Barnaby Joyce as leader of the Nationals. ( AAP: Mick Tsikas )

The new leader has a much lower profile than Mr Joyce.

His colleague John 'Wacka' Williams said he was sure that "as time goes on, Michael McCormack will get very well known".

"As time goes on he will build his profile," Senator Williams said.