Human rights group Amnesty International challenged European politicians attending tomorrow’s summit on refugees perishing in the Mediterranean to immediately establish an effective operation to save lives at sea.

They must authorise the immediate deployment of sufficient naval and aerial resources along the main migration routes to rescue people, Amnesty insisted yesterday.

Until this is in place, European governments should urgently provide Italy and Malta with financial and logistical support enabling them to step up their search-and-rescue capacity.

Amnesty’s Europe and Central Asia director John Dalhuisen said: “European leaders gathering in Brussels have an historic opportunity to end a spiralling humanitarian tragedy of titanic proportions.

“Europe’s negligence in failing to save thousands of migrants and refugees who run into peril in the Mediterranean has been akin to firefighters refusing to save people jumping from a towering inferno.

“Governments’ responsibility must clearly be not only to put out the fire but to catch those who have stepped off the ledge.”

Mr Dalhuisen’s comments followed an assessment by UN refugee agency UNHCR that more than 800 people drowned when a boat packed with migrants sank on Saturday.

Survivors gave the number of passengers on the three-deck trawler as 850, according to UNHCR spokesman Adrian Edwards in Geneva.

Only 24 bodies had been recovered, in addition to the 28 survivors.

“From available information and the various accounts we’ve had, UNHCR now believes the number of fatalities to have been over 800, making this the deadliest incident in the Mediterranean that we recorded,” said Mr Edwards.

The agency estimates that, so far this year, 1,776 refugees have died in the Mediterranean.

The newly arrived survivors told UNHCR that their boat had capsized after one of the crew crashed it against the Portuguese-flagged King Jacob container ship that had responded to a distress call.

“The survivors said that the person who was steering the boat, their smuggler, was navigating badly and he did a bad move that made it crash against the bigger ship,” said UNHCR spokeswoman Carlotta Sami in Sicily.

Prosecutors in the Italian city of Catania said yesterday that they had arrested the captain and a crew member of the people-traffickers’ trawler.