Italy has threatened to send nearly 180 migrants stranded on an Italian coastguard vessel “back to Libya” if Europe does not help, in a dramatic escalation of a crisis in the Mediterranean.

Some 177 people have been sitting off the coast of Lampedusa since Thursday after the coastguard’s Diciotti ship fished them out of the Mediterranean from smuggling dinghies bound for Europe.

Italy has been battling with Malta over who should take them in, deepening a bitter spat between the two countries.

Matteo Salvini, Italy’s far-right deputy prime minister, has now vowed to send them back to Libya, a country in the grips of a four year civil conflict, if the European Union does not step in to help.

“Either Europe decides to seriously offer Italy some concrete help, beginning with for example the 180 immigrants on board the Diciotti ship, or we will be forced to do what will definitively end the human traffickers’ business,” Mr Salvini said in a statement.

“That means taking the people saved in the sea back to Libya.”

Rescue ship Aquarius waits for port of safety for 141 migrants saved in the Mediterranean

Migrants in Libya face kidnapping, extortion, torture and slavery at the hands of heavily armed traffickers who have exploited a total breakdown in security to expand their trafficking networks. The migrants, who are often fleeing war or poverty back home, also regularly face abuse in the country’s detention centres, which are overflowing and poorly funded.

Since 2014, Libya has been roughly split in two between east and west as rival brigades of ex-rebels have fought each other for territory.

Amid the chaos, hundreds of thousands of migrants, desperate to seek a better life in Europe, have attempted the treacherous sea crossing from Libya.

Italy has borne the brunt of the crisis: since 2014 more than 650,000 migrants have landed on its shores. But after the election of a populist government in June it has started turning away rescue boats, arguing that other European countries should take their share of the load.

This year just over 19,000 migrants, hailing mostly from Tunisia, Eritrea and Sudan, have sailed to Italy, which is a record low. In contrast more than 26,000 have landed in Spain, three times the number that landed in the same period last year, as migrants have looked to other routes.

The Diciotti has been moored off Lampedusa since Thursday while the Italian authorities demanded that Malta take in the passengers.

Last week Malta allowed 141 migrants aboard French rescue boat the Aquarius to dock after an agreement to distribute them to a number of European countries.

However, Joseph Muscat, Malta’s prime minister, argued that this boat was not in distress and that the migrants had refused help.

Maltese interior minister Michael Farrugia meanwhile said the Diciotti picked up the migrants inside the Maltese search and rescue area “without any coordination from the competent RCC (Rescue Coordination Centre), just to stop them arriving in Italian waters”.

“An interception of a boat that exercises its right to free navigation in the high seas is not considered a rescue operation,” Mr Farrugia wrote on Twitter.

Migrants stranded on Greek island Show all 11 1 /11 Migrants stranded on Greek island Migrants stranded on Greek island Afghan Abdul Samad travelled to Greece on a dinghy Reuters Migrants stranded on Greek island A refugee carries his lunch provided by the Greek authorities Reuters Migrants stranded on Greek island A Syrian family sits around a bonfire at a makeshift camp Reuters Migrants stranded on Greek island The Moria camp for refugees and migrants on the island of Lesbos Reuters Migrants stranded on Greek island Iraqi refugee Shahed Naji, 22, who arrived in Moria five months ago Reuters Migrants stranded on Greek island Tombstones for refugees and migrants near the village of Kato Tritos Reuters Migrants stranded on Greek island Arebi, a Syrian refugee, at the makeshift camp next to the Moria camp Reuters Migrants stranded on Greek island A migrant makes his way to the makeshift camp next to Moria Reuters Migrants stranded on Greek island A girl walks next to a self-made shower Reuters Migrants stranded on Greek island Refugees and migrants line up to receive their lunch provided by the Greek authorities Reuters Migrants stranded on Greek island Syrian refugee Muhammad, 42, fishes in the city of Mytilene Reuters

He added that the “only solution” therefore was that the new boat, carrying 177, be taken to Lampedusa or an Italian port.

The refusal has infuriated the Italian government, which was already angry the rescue operation was carried out by the Italian coastguard because they had not secured the approval of Rome first.

“Malta’s behaviour is once again unqualifiable and deserves sanction,” Italian minister of transport Danilo Toninelli said on Sunday.

“The EU needs to step forward and open its ports to solidarity, otherwise it has no reason to exist,” he added.

This week’s spat between Italy and Malta is the second in just over a month. It follows a furious battle only days ago over 450 people who were rescued from a fishing ship and taken aboard two EU border agency vessels. They were eventually allowed to disembark in Italy after five European countries agreed to take 50 people each.