The Government's decision to allow workers from EU accession countries to come and work in the UK has been a "tremendous success", Home Secretary David Blunkett said today.
He insisted the European countries that closed their borders to workers had simply encouraged the growth of clandestine working, undermining labour standards and legitimate employers.
Nearly 91,000 people from the new member states registered to work in Britain in the first five months after EU expansion.
Mr Blunkett told a TUC conference on migrant workers that the UK's worker registration scheme had given the lie to allegations made at the time of the enlargement that the country would be flooded with immigrants. Workers on the scheme had already contributed £120 million to GDP, and £20 to tax and national insurance contributions.
However, Conservative Shadow Home Secretary David Davis accused the Government of spinning the figures, highlighting Home Office predictions that the number of migrants arriving in the UK from the new EU accession countries would be between 5,000 and 13,000.
"Today we learn that in the first five months nearly 91,000 have registered to work," he said.
He warned that there were probably "many more" working illegally.
"Regardless of how the Government tries to spin these figures, the fact is our immigration system is still a shambles."
Mr Blunkett told the conference that the UK needed migrant labour to keep its "vibrant" economy running, and praised their "substantial" contribution to the nation's well-being.
He said opposition proposals for immigrant quotas would be unworkable, as such a "rigid" system would be unable to keep pace with the demands of employers and population changes, or take account of shortages in certain regions and sectors.
And he said Conservative Party chairman Liam Fox had "lied through his teeth" and tried to "whip up fear" about immigration in a radio interview last weekend.
Raids on businesses suspected of illegally using migrant workers had doubled, he said, and would be stepped up "quite dramatically" in coming months.
Mr Blunkett told the trade union audience - among them TUC head Brendan Barber - that they had to take up the challenge of convincing their members, many of whom were opposed to migrant workers, that immigration was a positive move. Current levels of opposition showed many workers were "not only lacking in facts but also fearful and in need of reassurance".