Volunteers on a German refugee rescue ship have been deployed to help a vessel chartered by far-right activists that became stranded in the Central Mediterranean.

Sea-Eye said Italian officials told their crew that the C-Star, operated by an anti-immigration group calling itself Defend Europe, had suffered a mechanical failure and could not manoeuvre.

A spokesperson for Sea-Eye, which is among those Defend Europe has accused of “colluding” with Libyan people smugglers, said it was prepared to offer any aid needed.

Michael Buschheuer, the chairman of Sea-Eye, said: “To help a ship in distress is the duty of anyone at sea, without regard for their origin, race, religion or beliefs.”

But when his ship approached the crew of the C-Star reportedly refused help.

“Sea-Eye took on a course towards the C-Star and got in contact with the right-wing extremists but they refused any help,” a spokesperson said.

“On the instructions of the Maritime Rescue Coordination Centre [in Rome], the Sea-Eye continued its search for shipwrecks and drownings.”

Defend Europe confirmed its ship was suffering a “minor technical problem” that was being resolved.

“C-Star developed a minor technical problem during the night,” a spokesperson said, saying that its engine was stopped so it could be fixed.

“This means that under [maritime laws to prevent collisions] the vessel is considered ‘not under command’ and information was sent out to vessels nearby in accordance with regulations.

“This problem is about to be resolved.”

Migrants receive life jackets as workers from Proactive Open Arms pull alongside their dinghy about 15 miles north of Sabratha, Libya (AP)

The group, an offshoot of the white nationalist Identitarian movement, crowdfunded its ship with claims it would target “criminal NGOs… that are nothing less than part of the international human trafficking ring”.

Defend Europe claims the rescuing of refugees from the Mediterranean Sea, where more than 2,400 men, women and children have drowned so far this year, is part of an “invasion” endangering the continent.

The mission has been beset with difficulties that saw it delayed by several weeks, switching the launch to Cyprus from Sicily, where anti-racist campaigners and journalists had gathered last month.

The C-Star, a chartered ship, was stopped in the Suez Canal for security checks before journeying to northern Cyprus, where crew members were arrested over people smuggling allegations.

They were later freed after claiming that Sri Lankan crew members on board were “apprentice sailors” who were supposed to disembark in Egypt.

Humanitarian groups raised concern that Defend Europe could endanger lives in the Central Mediterranean if it interrupts rescue missions, but the group now claims it is merely “monitoring” NGO activity and will conduct refugee rescues if needed.

So far, activists on board have been shouting at humanitarian ships through megaphones and “trolling” other crews including the Spanish charity Provactiva Open Arms over radio by ordering them to leave the search and rescue zone.

In pictures: A day of refugee rescues in the Mediterranean Sea Show all 7 1 /7 In pictures: A day of refugee rescues in the Mediterranean Sea In pictures: A day of refugee rescues in the Mediterranean Sea A baby being taken on to MSF's Bourbon Argos ship from a boat carrying 130 migrants and refugees Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A refugee boat carrying 101 people being rescued by MSF's Bourbon Argos Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A refugee boat carrying 101 people being rescued by MSF's Bourbon Argos all images by Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A baby among refugees on a boat carrying 185 people off the coast of Libya Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea Migrants and refugees sleeping after being rescued by MSF's Bourbon Argos ship Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A crew from MSF's Bourbon Argos ship rescuing a boat carrying 130 migrants and refugees off the coast of Libya, at sunrise Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A woman in a stretcher being lifted onto MSF's Bourbon Argos ship from a boat carrying 130 migrants and refugees off the coast of Libya Lizzie Dearden

Robert Timm, a German member of the group, told The Independent the C-Star would “not interfere” with humanitarian operations.

“If we are called, we will help,” he added. “But we would make sure that they [the migrants] don’t get to Europe.”

Mr Timm claimed the C-Star would take asylum seekers to the “closest safe African harbour” instead of Italy and named Tunis as a possibility, although Tunisian authorities are not believed to have agreed to the plan.

He refuted the far-right label applied to the group and called Defend Europe a “democratic movement”, adding: “You can be against net immigration to Europe and on the other hand you can be compassionate with the people that drown.

“From our prospective people don’t drown because of ‘Fortress Europe’, but these NGOs are working as a pull factor.”

The activist claimed his organisation would help enforce a controversial code of conduct imposed by Italy, which only three of eight groups operating rescue ships have so far signed.

Mr Timm claimed Defend Europe has “a lot of evidence” to support its position but studies including a recent report by a House of Lords committee have not found any proof of NGO activity causing increased deaths or crossings.

Research has found the EU’s Operation Sophia anti-smuggling mission could itself be increasing death rates by causing smugglers to switch from wooden vessels to flimsy dinghies that cannot survive the treacherous crossing to Italy.

Prosecutors in Sicily have ordered the seizure of one of eight humanitarian rescue ships operating in the Mediterranean – the Luventa – over allegations its crew had contact with Libyan smugglers.

Italian coastguard rescues refugee boat from Libya in the Mediterranean

Ambrogio Cartosio, a public prosecutor from Trapani, Italy, said there was evidence some members of German charity Jugend Rettet had contact with smugglers during one incident in September and two others in June. But he stressed that there was no evidence of the group receiving any money from Libyan traffickers and no indication of a wider conspiracy between the two groups – a favourite theory of the European far-right.

“My personal conviction was that the motive is humanitarian, exclusively humanitarian,” Mr Cartosio said. “It would be fantasy to say there was a coordinated plan between the NGOs and the Libyan traffickers.”

The EU is training and equipping the Libyan coastguard, which is itself accused of killing, beating and abusing migrants, and has given millions of pounds towards detention centres and other controls by the fragile Libyan Government of National Accord.

The United Nations has warned of widespread rape, abuse, forced labour, kidnapping and ransom in the country, where smugglers have expanded a profitable trade in the chaos of the continuing Libyan civil war.