Anti-immigrant rhetoric from politicians across Europe, including Britain, is blocking attempts to introduce large search-and-rescue operations in the Mediterranean that would save large numbers of migrant lives, a senior UN official has warned.

In comments that reveal the growing frustration within the UN Refugee Agency over Europe’s response to the growing migration crisis in the Mediterranean, Laurens Jolles said political expediency was preventing measures being taken to reduce migrant deaths.

Jolles, the United Nations High Commissioner for Refugees (UNHCR) representative in Italy, said: “In many countries in Europe at the moment, the [political] dialogue and the rhetoric is quite extreme and very irresponsible.”

Italy is experiencing a wave of hostility towards the influx of migrants before regional elections at the end of May, while in the runup to the UK general election, Ukip has been accused of forcing a toxic debate about immigration and national identity.

Jolles said: “Because of elections and because of the economic crisis, it becomes difficult for those parties who traditionally would not follow on those same lines to counter the rhetoric with the strength that they should.

“It’s a fear of foreigners, which is a logical fear, a natural fear, but it is being exploited for populist or political reasons, especially in election periods.”

An estimated 400 migrants drowned last week when their boat capsized en route from Libya to Italy. The tragedy prompted fresh calls from human rights organisations to mount large-scale search-and-rescue operations, but UNHCR officials say politicians are choosing to avoid upsetting their electorates. “The level of this dialogue compared to 20 years ago is just incredible. It wouldn’t have been possible in the past, the racist rhetoric, the rhetoric of intolerance. In the 60s, 70s and the 80s, we would never have accepted this,” said Jolles.

Critics say the cancellation last year of an Italian-run sea rescue mission, Mare Nostrum, and the launch in November of Triton, a significantly smaller border surveillance operation by the EU, have created the conditions for what many believe will lead to a record number of migrant deaths in the Mediterranean this year.

EU governments believe the narrower scope of the current mission is justified, claiming that a scaled-back rescue operation will deter migrants from making the crossing.

The Foreign Office says it will not support future search-and-rescue operations because they encourage migration.

“The fact that the UK has made it clear that it does not wish to participate in contributing measures to a rescue operation, or putting in place a rescue operation in the Mediterranean, is very concerning,” said Jolles.

In December, the UNHCR appealed to the EU to provide 130,000 resettlement places for Syrians displaced by the civil war. Germany has pledged to take 30,000 and Sweden 2,700. The remaining 26 EU states are taking 5,438 between them, with Britain taking just 143. “The UK should be participating and contributing in a European context to solidarity measures and trying to fulfil its part making it easier to deal with these [migration] flows,” said Jolles.

“If one really wants to tackle the problem and ensure that there are less deaths, then the thing to do is to look at providing legal avenues to come to Europe. There is an obligation, both moral and legal, to try and do something. People will die.”

The European commission has drawn up a policy document, the European Agenda on Migration, due to be presented to member states next month, aimed at establishing a concerted European asylum policy. It more clearly defines conditions for legal migration, while formulating “a clear plan to fight smuggling and trafficking of migrants and an effective return policy”.The UNHCR is concerned that rather than helping to create a safe passage for migrants, the commission is more concerned with trying to stop people entering. “What we are hearing is that there is more dialogue on how to prevent people coming to Europe and how to stop them than how to manage the flows and what to do when these persons come into Europe,” said Jolles.