Italian Prime Minister Giuseppe Conte has accused his far-right interior minister and deputy prime minister, Matteo Salvini, of disloyalty and being obsessed with blocking immigration, intensifying an open war of words in the ruling coalition.
The renewed political turmoil threatens to derail preparations for the 2020 budget in the autumn, as Italy attempts to rein in its huge public debt.
A former academic who does not belong to any party, Conte on Thursday used the case of a migrant rescue boat refused entry to Italy's ports by Salvini as an opportunity to settle scores with the leader of the coruling League party, which last week put forward a motion of no confidence in his government coalition with the populist 5-Star Movement.
More than 500 migrants and refugees have been stranded on board two rescue boats in the Mediterranean since aid workers pulled them from the waters earlier this month. About 350 are thought to be on board the Ocean Viking and a further 150 on the Open Arms.
Salvini's League pushed a law through parliament last week which criminalised rescue workers and stated that any vessels carrying undocumented migrants in Italian waters could be seized, impounded and the crews prosecuted - with fines of up to $1.1m.
In an open letter to the interior minister, the Italian prime minister said he had convinced six EU states to take in the migrants on board the Open Arms charity ship and accused him of "disloyal collaboration" by misrepresenting Conte's own position.
Conte said Salvini aimed to exploit the immigration issue for electoral gain rather than seeking solutions with Italy's partners.
"I understand your faithful and obsessive concentration on addressing the issue of immigration by reducing it to the formula of 'closed ports'. You are a political leader and you are legitimately intent on constantly increasing your support," he wrote.
The Open Arms, operated by a Spanish charity, was in Italian territorial waters on Thursday, a day after a Rome administrative court gave it leave to enter, countermanding Salvini's ban.
Those still on board the Open Arms say they will only celebrate once they reach the shore.
"We need to touch ground," one passenger told Spanish broadcaster TVE. "Life is over there, here it's death."
Salvini issued an emergency order to prevent Open Arms arriving at the Italian island of Lampedusa. But the defence minister, who is from the League's partner party 5-Star, refused to countersign it.
Openly challenging the League leader, who has so far dictated Italy's immigration policy, Elisabetta Trenta said defying the court was illegal and that "politics must not lose its humanity".
The tide may have turned for Salvini, who last week was riding a wave of popularity so successfully he called for early elections in a bid to seize power for the far-right.
But his gamble has not gone to plan.
5-Star and the opposition Democratic Party have stalled any debate of the League's no-confidence motion and many of their politicians are now openly discussing forming a coalition among themselves to sideline Salvini.
The 5-Star has been hurt by its tie-up with the League, halving its voter support since the two parties joined forces in June last year, according to opinion polls. The League has overtaken it to become Italy's most popular party.
With the prospect of a 5-Star/Democrat government looking increasingly plausible, the League's Agriculture Minister Gian Marco Centinaio said on Wednesday he had not ruled out trying to patch things up with the coalition partner.
"I would never close the door completely," he said in a radio interview.
Salvini said on Wednesday the League would "do whatever we can to prevent a trickster's deal between 5-Star and the [Democrats]".
But in a hard-hitting Facebook post on Thursday, 5-Star leader Luigi Di Maio said there was no turning back after Salvini's move to pull the plug on the coalition.
"Now he regrets it, but the damage is done. Everyone creates their own destiny. Good luck!," Di Maio wrote.
League Cabinet Deputy Secretary Giancarlo Giorgetti, Salvini's closest aide, acknowledged in an interview in the La Repubblica daily on Thursday that the party could now end up in opposition.
"We could have held on to our government posts and now we risk looking stupid, but we posed a political issue," Giorgetti said.