Authority is a very delicate commodity. Abuse it and it becomes unrespected authoritarianism. Fail to nurture it and it withers.

Authority is now Barnaby Joyce's gravest problem.

When certain Nationals were strolling about late last year threatening to cross the floor in support of a royal commission into the banks, Mr Joyce was in no position to bring them to heel — even if he'd wanted to.

As more than one National noted, Barnaby was in no position to lecture them, having crossed the floor 47 times himself.

Barnaby Joyce was very different from his recent predecessors. ( AAP: Tracey Nearmy )

Indeed, for most of his time in federal politics, being the maverick, the freewheeling say-it-as-you-see it bloke was his greatest asset.

He was the rebel-within-a-cause who won regard outside of the political game as much he caused concern inside it.

These were the qualities and reputation he brought to the Nationals leadership. They were why his ascension was a prospect that worried some of his colleagues even though they knew it would invigorate.

Barnaby Joyce is very different from his recent predecessors. Nothing like the affable but reliable blandness of Warren Truss or the suave rural intellectualism of John Anderson.

And he's the antithesis of the somewhat forgettable Mark Vaile.

7.30 interview compounded the hurt

Sorry, this video has expired "Probably one of the greatest failures of my life" says Barnaby Joyce

This difference and Barnaby's uniqueness has been routinely celebrated by his Liberal mates.

Tony Abbott praised him as the nation's best retail politician. His knockabout larrikinism made his commentary raw and genuine.

And seemingly trustworthy.

The scandal that erupted about his personal life shattered the Barnaby mystique. Now seen by his Nationals colleagues as a philanderer who cheated on his wife of 24 years, he has lost moral authority.

That moral authority was further eroded, according to several of his parliamentary colleagues, in his interview with Leigh Sales.

It totally lacked contrition. He made no mention of his wife Natalie or daughters. There was no apology. It was selfish and self-serving.

Even Vikki Campion, the former staffer now expecting his child, was reduced to a "pregnant lady walking across the road".

It was an appalling outing for the Deputy Prime Minister.

An apology to his wife, at last

Judging by Mr Joyce's statement on Tuesday, he now recognises how awful that interview was.

In a monologue to an ABC camera he strenuously rejected new allegations of inappropriate behaviour involving a pinched bottom at a rural awards event.

He said it never happened.

"On another issue, I would like to say to Natalie how deeply sorry I am for all the hurt this has caused," he said.

"To my girls, how deeply sorry I am for all the hurt that it has caused them. To Vikki Campion, how deeply sorry I am that she has been dragged into this."

They were words that sought to belatedly plug the haemorrhaging respect.

Barnaby Joyce is a diminished political figure. His future as Nationals leader is doubtful.

And the Nationals' dogs are barking. Who will step up?