Lord Ashdown has called for military operations to destroy smugglers' boats before they can leave the coasts of Libya, after EU foreign ministers pledged to step up action against people trafficking networks.

The former Royal Marine told the Guardian: "It is unsustainable and unacceptable to have a policy of drowning refugees when we should be attacking the smugglers. We should be helping countries like Libya, Egypt and Tunisia, the departing nations, to attack people smugglers.

"There may also be a case for using special forces of interdiction to destroy the boats before they leave port."

At an emergency meeting in Luxembourg on 20 April, ministers agreed to a 10-point plan to tackle the escalating migration crisis, with more than 800 people believed to have died after a vessel capsized crossing the Mediterranean.

Among measures agreed on was "a systematic effort to capture and destroy vessels used by the smugglers", and European immigration and law enforcement agencies to work together to "meet regularly and work closely to gather information on smugglers modus operandi, to trace their funds and to assist in their investigation".

They also proposed increasing funding for patrols and expanding their area of operation, after the Italian-led Mare Nostrum programme was scrapped in 2014 in favour of a dramatically scaled back EU border patrol operation, Triton.

Labour leader Ed Miliband called for full search and rescue operations to be reinstated. He said: "I believe all of us have been shocked and appalled by events in the Mediterranean. We cannot stand by as people drown in European waters simply to escape conflict in Libya and Syria.

"It was wrong to end the search-and-rescue operations and they should be immediately restarted. We must recognise our humanitarian responsibility. If I was prime minister, I would be working with other European leaders to act.

"Our country is known throughout the world for our generosity of spirit. It's time to reflect that and take action in the face of this terrible tragedy."

The European Union has been "very deficient" in the way it has handled the problem of migrants fleeing over the Mediterranean to Europe, Deputy Prime Minister Nick Clegg has said. The Lib Dem leader said the EU had a "shared responsibility" to find a solution.

Ukip leader Nigel Farage said though he supported Britain in providing assistance to people in "beleaguered countries", it "could not share the problems of all the other countries" in the EU.