Image caption Ambassador Daniele Mancini had given his personal assurance that the marines would return on time

India's Supreme Court has said Italy's envoy does not have legal immunity, in an escalating row over Rome's refusal to return two marines charged with murdering two Indian fishermen.

India's Chief Justice Altamas Kabir said the court had "lost trust" in Italy's ambassador Daniele Mancini.

The court reiterated last week's order for him not to leave the country.

The marines were allowed to go home to vote in last month's polls on condition that they return to stand trial.

International Law Diplomats enjoy immunity from criminal jurisdiction of the receiving state

Only the sending state can waive diplomatic immunity

Exemptions under civil and administrative jurisdiction mainly concern commercial activity Source: Vienna Convention on Diplomatic Relations

Mr Mancini had given his personal assurance that the two marines - Massimilian Latorre and Salvatore Girone - would return within four weeks as ruled by the court.

There has been no comment from the Italian embassy in Delhi or Ambassador Mancini.

But on Friday, Rome said it was seeking a "friendly agreement" with India to resolve the row.

The office of President Giorgio Napolitano said Italy wanted an agreement based on "international law".

'Mistook for pirates'

Analysis The stand-off between Delhi and Rome over the Italian marines skipping bail goes on - with two fatherless families stuck in the middle of an international row. India's Supreme Court insists the ambassador effectively handed in his diplomatic immunity with his affidavit promising their return. Yet, India could enter murky legal waters if it tried to stop the ambassador going. Italy may have breached international law by breaking its promise, experts argue, but the ambassador still has diplomatic protection The UK government had to back down on threats to lift the immunity of the Ecuadorean embassy in London after Wikileaks founder Julian Assange took shelter there. But Italy's actions have caused such fury here, the Indian government has to stand firm. So unless there's a compromise deal, India may now use its right under the Vienna convention on diplomatic relations to expel the ambassador.

In its order on Monday, the three-judge Supreme Court bench said Ambassador Mancini, who had negotiated the marines' release, had waived his immunity by giving an undertaking to a court that the pair would return.

"A person who comes to court and gives an undertaking has no immunity," Chief Justice Kabir said.

The court set 2 April as the next date of hearing and restrained the Italian ambassador from leaving India "until further orders".

The marines are accused of shooting the fishermen in Kerala in February 2012. They said they mistook them for pirates.

Rome says it wants its nationals to be tried in Italy. Italy believes India has no jurisdiction in the case, saying the incident took place in international waters,

India has said that irrespective of the location of the ship, it has the right to try the marines as the fishermen were unarmed Indians on board an Indian fishing boat.

Prime Minister Manmohan Singh warned that "there will be consequences" unless Italy returned the marines.

In unusually strong language, the prime minister said Italy's refusal to do so was "unacceptable".