The Turnbull Government has sailed into a political crisis of its own creation, and one of its co-captains will have to walk the plank.

The Coalition's hold on power now hinges on two warring, obstinate leaders mending a ripped relationship.

Malcom Turnbull's partnership with Barnaby Joyce has, until recently, had a veneer of folksy mateship. But the Prime Minister's excoriation of Mr Joyce on Thursday lifted that veneer, exposing a raw enmity between the two.

In announcing a ban on ministers having sex with their staffers, the PM was seeking to draw a line under an ugly episode that has brought the entire political institution into disrepute.

And while Mr Turnbull's "bonk ban" edict risks weaponising sexual misconduct claims on Capital Hill, by making intraoffice sex a sackable offence, he was also pronouncing judgement on the Nationals leader's character.

Sorry, this video has expired 'A shocking error of judgement'

The Deputy Prime Minister's affair with press officer Vikki Campion was a "shocking error of judgement," the PM said, and that Mr Joyce should "obviously" consider his position.

It was an astonishing, public repudiation. A vote of no confidence in his deputy.

He was imploring Mr Joyce to sack himself, knowing the Coalition arrangement renders him unable to sack the Deputy PM himself.

Mr Turnbull clearly misjudged Mr Joyce's stubbornness. Instead of quietly taking personal leave, as asked of him, the former bouncer who once lost his front teeth in an Armidale pub simply shoved back.

His squabble with Mr Turnbull now has all the elegance of Friday night biffo at the Wicklow Hotel.

Mr Joyce has not only doubled down in his resistance, but cast his own harsh verdict on Mr Turnbull.

His vicious return of serve amounted to a vote of no confidence in the Prime Minister, saying Mr Turnbull's comments were "inept" and "unnecessary".

Mr Joyce may have lost his moral authority as a national leader, but he was not going to respect the PM's authority.

This split has the potential to be fatal for the Government.

If the two bulls don't heal their relationship — and fast — the paddock fences will be broken.

A Nationals revolt against the PM has its obvious dangers in a one-seat majority.

Sorry, this video has expired Barnaby Joyce hits back at Malcolm Turnbull's criticism of his conduct as "unnecessary" and "inept"

Mr Turnbull's initial response to Mr Joyce suggests he won't be backing off, even if his tone was more conciliatory, but what's said can't be unsaid.

This schism needs resolving before the PM heads to Washington next week, because on his return, he would begin a parliamentary week with his numbers immediately put to the test.

One way or another, Barnaby Joyce is cooked. The question is whether the rest of the Nationals let the Government get cooked with him.