The Foreign Secretary faces criticism for saying "marauding" migrants threaten Europe's standard of living.
Foreign Secretary Philip Hammond says an influx in African migrants will undermine living standards and social cohesion across Europe.
Speaking on a visit to Singapore, he warned the EU could not afford to absorb "millions" of African migrants.
Mr Hammond said EU laws need to be changed to ensure people are returned to their native country if they are simply seeking a better way of life.
"We have got to be able to resolve this problem ultimately by being able to return those who are not entitled to claim asylum back to their countries of origin," he told BBC News.
"That's our number one priority."
But his comments - some of his most outspoken remarks on the issue - have been condemned as "mean-spirited" and "shameful" and described as "scaremongering".
Mr Hammond said there would always be an "economic motivation" for Africans to try to reach Europe and the current laws mean they are "pretty confident" they can stay.
"As long as the Europe Union's laws are the way they are, many of them will only have to set foot in Europe to be pretty confident that they will never be returned to their country of origin," he said.
"Now, that is not a sustainable situation because Europe can't protect itself and preserve its standard of living and social structure if it has to absorb millions of migrants from Africa."
Mr Hammond said ensuring migrants could be returned to their country of origin would help fix the Calais "crisis".
Around 5,000 people are camped around the French port town, many attempting to make it to Britain through the Channel Tunnel.
It is a perilous way to make it to Britain, with at least nine people killed in the tunnel last month.
Mr Hammond said: "So long as there are large numbers of pretty desperate migrants marauding around the area there will always be a threat to the tunnel's security."
The UK Government has promised to boost security in Calais by sending additional security guards, sniffer dogs, fences and surveillance equipment including more CCTV.
On Sunday police discovered 17 suspected illegal immigrants hiding in the back of a lorry on the M1.
Shadow foreign secretary Hilary Benn strongly criticised Mr Hammond's comments.
"We need responsibility and international leadership from this government, not scaremongering," Mr Benn said.
"Those fleeing Syria are desperate refugees from a country being torn apart by war.
"Philip Hammond should think more carefully about what he says."
Steve Symonds from Amnesty International UK said Mr Hammond's comments were "shameful".
"Rather than throwing up the drawbridge and talking about how Europe can 'protect' itself from migrants, Mr Hammond should be working with our EU partners to ensure that people don't drown in the Mediterranean or get crushed beneath lorries at Calais," he said.
"With countries like Lebanon, Ethiopia and Chad hosting far more refugees than the UK and other European countries, the Foreign Secretary's mean-spirited response is shameful."
It comes after David Cameron was criticised last month for describing migrants as a "swarm" trying to get to Britain.
Courtesy: Sky News