Discussions are underway within the National Party about formally tapping Barnaby Joyce on the shoulder and asking him to resign.

Key points: Senior Nationals have been approached to ask Barnaby Joyce to stand down from party leadership

Senior Nationals have been approached to ask Barnaby Joyce to stand down from party leadership One person refused to be part of any delegation calling for his resignation, and instead visited him privately

One person refused to be part of any delegation calling for his resignation, and instead visited him privately Nationals have told the ABC they would prefer Mr Joyce step aside, rather than a leadership challenge

Senior Nationals have been approached to form part of a delegation to ask the Deputy Prime Minister to step down.

Mr Joyce has not yet been visited by a delegation, but one senior Nationals figure refused to be part of any such group, instead choosing to visit the Nationals leader privately.

A sizeable portion of the National Party wants Mr Joyce to step aside, and they have been turning their attention to who should replace him.

Nationals MPs and senators say his reputation has been so badly damaged by his affair with former media advisor Vikki Campion, he cannot regain credibility.

Former Nationals leader Warren Truss told ABC's 7.30 he was sure members of Parliament were assessing whether Mr Joyce should resign in the interests of the party and the Government.

"The reality is that is a decision for the Nationals party room. Barnaby has undoubtedly been diminished as a result of what has happened," Mr Truss said.

"But he still has enormous capabilities and if he chooses to and he wants to, I am sure he could still be a very good deputy prime minister."

Mr Truss said the issue certainly needed to be resolved and resolved quickly.

Sorry, this video has expired Warren Truss says Barnaby Joyce's leadership is 'diminished' ( Leigh Sales )

Senior LNP senator Ian Macdonald, speaking on 7.30, refused to endorse Mr Joyce as acting prime minister next week when Prime Minister Malcolm Turnbull is overseas.

"It's going to be difficult for Barnaby," he said.

"It's a very difficult time for him personally and I feel for him.

"In the role as acting prime minister it's going to be difficult for him to focus on things that he would want to focus on as Australia's acting leader."

Throughout his entire career, Mr Joyce has won votes because of his colourful and charismatic approach.

But now it is widely felt within the National Party that Mr Joyce's greatest political asset — his authenticity and believability — is in tatters.

He said on Tuesday he would remain as Nationals leader and he is widely regarded as a "survivor". As one Nationals MP said, Mr Joyce would "survive in a desert without water".

In any case, he will be desperately determined to cling on to the leadership and would have to be blasted out.

His determination to keep to his job makes the Nationals' hope of a smooth transition an unlikely outcome, meaning this will either drag on or get even nastier.

The Nationals do not like the idea of a leadership challenge because they do not want blood on their hands, and it conflicts with their party's tradition.

But they are tired of fielding phone calls from disgruntled voters who are deeply disappointed and furious with the Deputy Prime Minister's behaviour.

As yet, no-one in the party has approached Mr Joyce to tell him he should resign.

It is still "up in the air", one Nationals MP said. Another added it would "probably" be dealt with this week.

One looming problem for the Coalition is that Mr Joyce is meant to be acting Prime Minister next week. ( ABC News: Jed Cooper )

McCormack tipped to replace Joyce if he resigns

As tensions over the scandal boil furiously within Coalition ranks, Nationals are suggesting Michael McCormack would be a suitable successor and party leader.

Mr McCormack is the member for the New South Wales seat of Riverina and is Minister for Veterans Affairs.

He is regarded as a steady set of hands who would be a capable, reliable and sensible leader.

He twice lost out on winning the deputy leadership, once to former senator Fiona Nash and late last year, to Victorian senator Bridget McKenzie.

There is a feeling within the party that if Mr Joyce resigned or was rolled in a leadership challenge, Bridget McKenzie would remain as deputy leader.

That would make it difficult for Victorian MP Darren Chester, who was controversially sacked from cabinet by Mr Joyce last year, to be elected to a leadership position.

The Nationals would not want two Victorians leading their party.

Some are suggesting Michael McCormack (L) could be a suitable successor. ( ABC News: Adam Kennedy )

Liberals predict Nats will roll Joyce

Liberal MPs have told the ABC they were furious about the way the Barnaby Joyce saga has damaged the Coalition.

They predict the Nationals party room will remove him, but add that the situation was still fluid, and the decision was not up to them.

But the other looming problem for the Coalition is that Mr Joyce is meant to be acting Prime Minister next week.

There is no appetite for that within the Coalition, given it would fuel an already raging fire.

That is why the senior Liberal arm of the Coalition may end up flexing its muscle to pressure Mr Joyce to resign.