Developed nations must be prepared to become more culturally diverse in order to fill job vacancies caused by their ageing societies, a leading think-tank chief said today.

William Lacy Swing, the head of the International Organization for Migration (IOM), said ageing societies in the developed world and endemic youth unemployment in developing countries would drive demographic trends.

Speaking at a meeting on migration in Cairo, Mr Swing said 'northern' societies need workers while 'we have a youthful, largely unemployed global south, with young people needing jobs.'

Mr Swing, a former United States ambassador and United Nations under-secretary general, said the world is bound to become more diverse in terms of culture, ethnicity and religion.

William Lacy Swing, the head of the International Organization for Migration, has warned world leaders that they must be willing to become more culturally diverse because they need workers

He said: 'Leaders who are not preparing their people for this, through public education, public information, and awareness-raising campaigns, just may not be doing their job.'

The IOM is a British-based organisation that works with government's around the world to to promote humane and orderly migration.

Mr Swing's comments come as Europe faces its biggest migration crisis since the Second World War, with thousands of refugees pouring into every day from war-torn countries in the Middle East and Africa.

More than half a million have arrived by sea in Greece this year and the rate of arrivals is rising with over 8,000 coming on Monday alone in a rush to beat the onset of freezing winter, the United Nations said on Tuesday.

In all, more than 643,000 refugees and migrants from the Middle East, Africa and Asia have crossed the Mediterranean to Europe this year and at least 3,135 have died en route, according to the U.N. High Commissioner for Refugees.

Germany in particular – which has agreed to accept around one million asylum seekers this year alone – has open to accepting migrants into their society.

March of the migrants: Around 2,000 refugees are escorted by the Slovenian police as they walk towards the refugee camp in Brezice, Slovenia

Crisis: The European Union's executive has summoned leaders of the countries on the migrant trail to a summit in Brussels on Sunday in an effort to better co-ordinate the flow from one country to another

But others have shut their borders or imposed daily limits on numbers, saying they can't cope with the massive influx entering the country.

Last month, the EU approved plans to relocate 160,000 asylum seekers from overstretched frontline states Italy and Greece with a compulsory quota system that was fiercely opposed by some eastern, more hardline members of the bloc.

The plan requires most of the 28 member states accept a share of those people over the course of two years.

But so far, only 19 Eritrean asylum seekers have been relocated from Italy to Sweden although another 100 people are due to be flown to other cities in the coming days.

Out of the 23 member states that are legally required to admit a share of the human burden, only six have offered immediate places so far – Austria, France, Germany, Luxembourg, Spain and Sweden, the source said.

Member states have also been slow to follow up with promised financial help – out of the €2.8billion pledged at an emergency EU summit on September 23, only about €474million has materialised.