The death rate among migrants attempting to cross the Mediterranean to enter Europe has almost doubled over the past year.

Comparing the first five months of this year with the same period last year, UN agency data reveals that the mortality rate grew from 1.2% to 2.3%. The death rate during all of 2015 was 0.37% – a sixth of its current level.

Details of the drownings came as it emerged that far-right activists are planning to send boats to the Mediterranean this summer to disrupt search-and-rescue vessels that are attempting to save the lives of refugees.

Thousand of migrants are still stranded on Greek islands. Photograph: Louisa Gouliamaki/AFP/Getty

The new figures prompted calls for the international community to stop turning a blind eye to the unfolding crisis. Aid agencies said the rising death rate was caused by a shortage of search-and-rescue vessels and the increasingly unsafe boats being provided by smugglers and traffickers in Libya.

Last week a Médecins Sans Frontières (MSF) vessel rescued 1,500 people in 10 hours, more than double the boat’s capacity. Vickie Hawkins, executive director of MSF UK, accused world leaders of turning their backs on refugees and choosing to focus on border security instead of adopting a humanitarian approach that would lower the Med’s death toll.

“The deterrence policies implemented to keep people away from Europe have little regard for the human consequences. As a result, the Mediterranean has turned into a giant cemetery with over 1,500 missing or dead so far this year and tens of thousands of people detained inside Libya.”

Leonard Doyle, chief spokesman for the UN migration agency, the IOM, said it had detected a hardening of attitude towards economic migrants from Africa, who were looking for work as they moved north towards Europe. “These are impoverished, black, sub-saharan Africans and there’s definitely less interest in them and less warmth towards them than there was towards the refugees coming in from Syria last year, there’s no question about that,” said Doyle.

He added: “The rate of deaths has gone sky high. People looking for work are being told to get into a dinghy and they’ll get a job. These are very vulnerable people ending up in exploitative situations.”

During the first five months of last year the IOM recorded 205,858 migrants reaching Europe via the Mediterranean with 2,512 deaths. So far this year a far smaller amount – 71,029 – of migrants and refugees have crossed the Med to enter Europe yet the number of deaths stands at 1,650.

Research by the University of Warwick published last week – the first large-scale comparative study of the backgrounds and aspirations of refugees and migrants heading for Europe – challenged the prevailing view that they pick Europe as their destination of choice. Instead, researchers found that many did not even know anything about the EU prior to their arrival and had in fact been manipulated by traffickers who promised them work.

Thousands of asylum seekers remain stranded on Greek islands as the “one in one out” EU-Turkey deal falters.