Britain will never "in a thousand years" agree to a common European immigration policy to deal with the surging number of refugees fleeing to the continent, a top government official declared Tuesday.

Home Secretary Theresa May, the U.K.'s interior minister, told an audience at the Conservative Party conference that Britain should tighten control of its borders, admitting vulnerable refugees but keeping out those who simply want a better life.

She said other European countries should also toughen up their border controls, arguing that in the last few years more people had applied for asylum in the EU from Balkan countries — which have not seen war for years — than from war-torn Syria.

She said Europe's immigration crisis "can only be resolved by nation states taking responsibility themselves — and protecting their own national borders."

May said the arrival in Europe of hundreds of thousands of migrants had "led some people to say we need a new approach, a new European approach that would involve a common immigration and asylum policy.

"To those people, I have a very clear answer: Not in a thousand years," May said.

In a tough speech on immigration, May said Britain would combine "hard-headed common sense with warm-hearted compassion."

She said "it's impossible to build a cohesive society" with the high levels of immigration that Britain has seen in the past decade. Net migration to the U.K. was 330,000 people in the year to March.

May is seen as a potential future Tory leader, and her speech was aimed at boosting her support within the party. Her hard tone differs from that of Prime Minister David Cameron, who stressed Tuesday that Britain needs and benefits from immigration, as long as it is controlled.

A leading business-owners' group, the Institute of Directors, criticized May's "irresponsible" rhetoric.

"It is yet another example of the Home Secretary turning away the world's best and brightest, putting internal party politics ahead of the country and helping our competitor economies instead of our own," said its director-general, Simon Walker.