Europe is facing a major humanitarian crisis as estimates say the numbers refugees and asylum seekers dying at sea is likely to soar as the summer “boat season” approaches.

Already this year about 42,000 people have attempted to cross the Mediterranean to Italy, according to the EU border agency

And United Nations estimates say there will be a sharp increase in migrants making the treacherous crossing in coming months.

The UN is considering establishing refugee holding centres in north Africa and the Middle East due to the soaring numbers of people attempting perilous journeys across the Mediterranean in a desperate effort to reach Europe.

Refugee agency the UNHCR, has said for the first time that the large-scale processing of migrants and refugees outside Europe, in countries such as Egypt, Libya or Sudan, may be necessary as frontline authorities claim they have been abandoned by Brussels in the face of a “colossal humanitarian catastrophe”.

Hundreds of thousands of people are preparing to make treacherous crossings on unseaworthy vessels from the north African coast to Greece and Italy as this summer’s “boat season” gets under way, reports say.

Figures for the first few months of this year already show a dramatic increase on previous years.

UNHCR’s European director, Vincent Cochetel, has told reporters: “We would not be totally against external processing if certain safeguards were in place: the right to appeal, fair process, the right to remain while appeals take place.”

The EU had not found effective mechanisms to prevent migrants dying at sea, he said. Instead of focusing on ever tougher border controls, the EU needed to establish safe routes.

Campaigners for refugee rights have so far rejected the idea of large processing camps outside Europe, fearing refugees would be at the mercy of states with poor records on human rights and justice.

But Greece, which currently holds the EU presidency, is pressing for the establishment of holding centres in north Africa and the Middle East in order to process refugees and migrants before they reach European soil.

The Greek government is also calling for an international seaborne taskforce to patrol the Mediterranean in an attempt to stem the flow of migrants.

Italy, meanwhile, has pledged to force the migrant issue to the top of the EU agenda when it takes over the presidency in July.

The shift in the UNHCR’s position – and growing pressure from Greece and Italy for action – comes as the latest figures show a rapidly accelerating problem.

Last week, more than 1,000 migrants stormed a razor-wire fence at Melilla, a Spanish enclave in Morocco, in order to reach European territory, 400 of whom breached the barrier.

The same day, French riot police bulldozed three camps holding hundreds of refugees in the port of Calais.

Numbers of refugees and asylum seekers have been swelled by large numbers of Syrian refugees seeking to escape the civil war, which has displaced millions of people in the past three years.

Around 7,000 refugees from Syria arrived on the Italian coast in the first nine months of 2013, compared with 350 in the whole of 2012. They are the second largest group to arrive by sea in Italy this year, after Eritreans. Most making boat journeys to Greece are Syrian refugees, including women and children.

In a statement condemning the EU’s inaction, Amnesty International said: “With virtually no safe and legal routes into Europe, people are increasingly pushed into the hands of smugglers and traffickers, and are forced to risk their lives on unseaworthy vessels.”

At least a third of refugees heading for Greece end up having to be rescued. Many boats are in poor condition and are overcrowded.

The cash-strapped Greek government said it spent €65m to protect the eastern seafront last year, with only €2m contributed by the EU.

Meanwhile, refugees in Sicily are being housed in makeshift accommodation, such as schools and sports halls, with inadequate reception and processing facilities.