Philip Hammond, the UK's Foreign Secretary, has accused African migrants seeking a better life in Europe of undermining the continent's "standard of living".
Speaking during a visit to Singapore, Mr Hammond said Britain's "number one priority" was to find a way to make it easier to send would-be asylum seekers back where they came from, adding that Europe could not "absorb millions of migrants from Africa".
He told BBC News that in many cases migrants knew they only needed to set foot in the EU to be confident they would never be forced to leave.
Mr Hammond made his comments as 19 suspected illegal immigrants were found in a single "suspicious" lorry travelling on the M1 near St Albans.
The lorry was stopped by police and the driver arrested on suspicion of assisting illegal entry to the UK. The men inside were also detained.
British Foreign Secretary Philip Hammond speaks in Tokyo, Saturday, Aug. 8, 2015
Asked about how Britain could solve the migrant "crisis" at Calais and prevent more people dying trying to cross the Mediterranean from north Africa, Mr Hammond said: "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. That's our number one priority.
"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.
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"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 also said more should be done to "enhance the physical security of the tunnel" at Calais, warning that "there are large numbers of pretty desperate migrants marauding around the area". In pictures: Calais crisis intensifies
His comments follow criticism of the UK by a UN's special rapporteur on the human rights, who said that Britain's approach to the "courageous" migrants at Calais is tantamount to "racism".
Speaking to The Sunday Times, envoy Francois Crepeau said there was little difference between the migrants and UK travellers taking a "vacation in Thailand".
"It is remarkable that in most of our countries we have nothing against numerous Germans and French coming in and we dislike profoundly that people with darker skin colours are coming in."
