European Union judges have banned Britain from deporting asylum seekers back to Greece.
In a significant ruling, the European Court of Justice held handing over would-be refugees could infringe their human rights.
It is believed transfer of asylum seekers to Greece was stopped earlier this year in anticipation of the ruling.
The ruling is significant as Greece is considered a key entry point over EU borders for illegal immigrants from Africa, Asia and the Middle East heading for Britain.
Responding to the verdict, Immigration Minister Damian Green said: “We are working with Greece to improve their asylum processes.”
A UK Border Agency spokesman: “We will consider the detail of this judgment carefully.”
Dubbing the decision as a “disgrace” and a “mockery”, some of the critics said the decision would piles pressure on over-stretched frontier controls.
Tory MP Priti Patel said: “This decision is an absolute disgrace that flies in the face of common sense. Once again, European judges are making a mockery of human rights.”
Alp Mehmet, of the think-tank MigrationWatch, said: “This is the sort of absurdity that we have come to expect from the European courts. Common sense should be applied here, but they have failed to show any.