Migrant workers are praised by Blunkett

Migrant workers make a "disproportionate" contribution to the economy, paying £2.5bn more in tax each year than they take out in services, David Blunkett said yesterday.

Calling for the country to lift "our sights above the difficulties of asylum and illegal immigration", he said the economy depended on attracting workers from overseas. Foreign-born people represented 8 per cent of the population, he said, but generated 10 per cent of the gross domestic product.

He said: "There must be rules which offer fair treatment to those who are fleeing persecution, but which are resistant to abuse, and which balance the rights of the individuals with the rights of society. No modern, successful country can afford to adopt an anti-immigration policy."

Speaking at the Royal Institute of International Affairs, he added: "It is in all our interests to harness the innovation, skills and productivity new migrants can bring."

Last night, Mr Blunkett told BBC2's Newsnight that he was planning a crackdown on bogus colleges that offered places to foreign students who then disappeared into the jobs black market. He disclosed that he and Charles Clarke, the Education Secretary, were preparing a drive against the fraudulent use of student visas.

"We're going to clamp down much more effectively on those people or institutes that are providing a cover for people coming into the country," he said, adding that300,000 foreign national students came to Britain each year, some of whom "disappear into a clandestine economy".