The EU and member states should be prosecuted for the deaths of thousands of migrants who drowned in the Mediterranean fleeing Libya, according to a detailed legal submission to the international criminal court (ICC).

The 245-page document calls for punitive action over the EU’s deterrence-based migration policy after 2014, which allegedly “intended to sacrifice the lives of migrants in distress at sea, with the sole objective of dissuading others in similar situation from seeking safe haven in Europe”.

The indictment is aimed at the EU and the member states that played a prominent role in the refugee crisis: Italy, Germany and France.

The stark accusation, that officials and politicians knowingly created the “world’s deadliest migration route” resulting in more than 12,000 people losing their lives, is made by experienced international lawyers.

The two main authors of the submission are Juan Branco, who formerly worked at the ICC as well as at France’s foreign affairs ministry, and Omer Shatz, an Israeli lawyer who teaches at Sciences Po university in Paris.

The allegation of “crimes against humanity” draws partially on internal papers from Frontex, the EU organisation charged with protecting the EU’s external borders, which, the lawyers say, warned that moving from the successful Italian rescue policy of Mare Nostrum could result in a “higher number of fatalities”.

The submission states that: “In order to stem migration flows from Libya at all costs … and in lieu of operating safe rescue and disembarkation as the law commands, the EU is orchestrating a policy of forced transfer to concentration camps-like detention facilities [in Libya] where atrocious crimes are committed.”

The switch from Mare Nostrum to a new policy from 2014, known as Triton (named after the Greek messenger god of the sea), is identified as a crucial moment “establishing undisputed mens rea [mental intention] for the alleged offences”.

It is claimed that the evidence in the dossier establishes criminal liability within the jurisdiction of the ICC for “causing the death of thousands of human beings per year, the refoulement [forcible return] of tens of thousands migrants attempting to flee Libya and the subsequent commission of murder, deportation, imprisonment, enslavement, torture, rape, persecution and other inhuman acts against them”.

The Triton policy introduced the “most lethal and organised attack against civilian population the ICC had jurisdiction over in its entire history,” the legal document asserts. “European Union and Member States’ officials had foreknowledge and full awareness of the lethal consequences of their conduct.”

The submission does not single out individual politicians or officials for specific responsibility but does quote diplomatic cables and comments from national leaders, including Angela Merkel and Emmanuel Macron.

The office of the prosecutor at the ICC is already investigating crimes in Libya but the main focus has been on the Libyan civil war, which erupted in 2011 and led to the removal of Muammar Gaddafi. Fatou Bensouda, the ICC prosecutor, has, however, already mentioned inquiries into “alleged crimes against migrants transiting through Libya”.

The Mare Nostrum search and rescue policy launched in October 2013, the submission says, was “in many ways hugely successful, rescuing 150,810 migrants over a 364-day period”.

Criticism of the policy began in mid-2014 on the grounds, it is said, that it was not having a sufficient humanitarian impact and that there was a desire to move from assistance at sea to assistance on land.

“EU officials sought to end Mare Nostrum to allegedly reduce the number of crossings and deaths,” the lawyers maintain. “However, these reasons should not be considered valid as the crossings were not reduced. And the death toll was 30-fold higher.”

The subsequent policy, Triton, only covered an “area up to 30 nautical miles from the Italian coastline of Lampedusa, leaving around 40 nautical miles of key distress area off the coast of Libya uncovered,” the submission states. It also deployed fewer vessels.

It is alleged EU officials “did not shy away from acknowledging that Triton was an inadequate replacement for Mare Nostrum”. An internal Frontex report from 28 August 2014, quoted by the lawyers, acknowledged that “the withdrawal of naval assets from the area, if not properly planned and announced well in advance – would likely result in a higher number of fatalities.”

The first mass drownings cited came on 22 January and 8 February 2015, which resulted in 365 deaths nearer to the Libyan coast. It is alleged that in one case, 29 of the deaths occurred from hypothermia during the 12-hour-long transport back to the Italian island of Lampedusa. During the “black week” of 12 to 18 April 2015, the submission says, two successive shipwrecks led to the deaths of 1,200 migrants.

As well as drownings, the forced return of an estimated 40,000 refugees allegedly left them at risk of “executions, torture and other systematic rights abuses” in militia-controlled camps in Libya.

“European Union officials were fully aware of the treatment of the migrants by the Libyan Coastguard and the fact that migrants would be taken ... to an unsafe port in Libya, where they would face immediate detention in the detention centers, a form of unlawful imprisonment in which murder, sexual assault, torture and other crimes were known by the European Union agents and officials to be common,” the submission states.

Overall, EU migration policies caused the deaths of “thousands civilians per year in the past five years and produced about 40,000 victims of crimes within the jurisdiction of the court in the past three years”, the report states.

The submission will be handed in to the ICC on Monday 3 June.

An EU spokesperson said the union could not comment on “non-existing” legal actions but added: “Our priority has always been and will continue to be protecting lives and ensuring humane and dignified treatment of everyone throughout the migratory routes. It’s a task where no single actor can ensure decisive change alone.

“All our action is based on international and European law. The European Union dialogue with Libyan authorities focuses on the respect for human rights of migrants and refugees, on promoting the work of UNHCR and IOM on the ground, and on pushing for the development of alternatives to detention, such as the setting up of safe spaces, to end the systematic and arbitrary detention system of migrants and refugees in Libya.

“Search and Rescue operations in the Mediterranean need to follow international law, and responsibility depends on where they take place. EU operations cannot enter Libya waters, they operate in international waters. SAR operations in Libyan territorial waters are Libyan responsibility.”

The spokesperson added that the EU has “pushed Libyan authorities to put in place mechanisms improving the treatment of the migrants rescued by the Libyan Coast Guard.”