Britain was one of the few countries to open its doors to workers from the ten new members of the European Union which joined in May 2004.
Most nations, such as France, Germany or Spain, imposed limits on migrant workers from the "accession states" of Poland, Lithuania, Latvia, Estonia, Cyprus, Malta, Hungary, Slovenia, Slovakia and the Czech Republic.
The United Kingdom, Ireland and Sweden bucked the trend, despite fears of large-scale population movement.
One of the arguments against restrictions was it would create two classes of EU member, with only the richer countries enjoying full membership.
Limits also undermined the creation of a genuine single market, supposedly one of the EU's goals.
David Blunkett, at that time the Home Secretary, said legal migration was the best way to fill vacancies in the labour market.
And he was backed by the Confederation of British Industry, which said "sensitively managed" migration made a huge contribution to the economic well-being of the country.
Pressure group Migration-watch, led by Sir Andrew Green, Britain's former ambassador to Saudi Arabia, ridiculed the Government's predictions that only 13,000 Eastern Europeans would come to Britain.
In the end, the level of migration has been much higher. But, perhaps surprisingly, many of the loudest complaints have come from the left.
Unions expressed concerns foreign workers would be underpaid or exploited, and could be in danger on construction sites if they couldn't speak or read English.
Others feared unacceptable pressure would be put on the health service and benefits system, British people would lose out on jobs and schools would struggle to cope with children speaking a range of foreign languages.
Commentator Polly Toynbee has used her newspaper column to warn repeatedly that immigration is making "the rich richer and the poor poorer".
The effect of immigration on the countries people leave is also increasingly seen as a problem.
Tim Haughton, of the European Research Institute at the University of Birmingham, warned that migration from former Communist states is good for Britain - but may hurt the countries workers emigrate from.
He said: "There have been significant benefits in a number of areas because of the arrival of new migrants.
"They have filled key shortages that we have, but they have also been willing to do work at the bottom of the employment scale that our people are not willing to do.
"The people who migrate tend to be healthy and highly-motivated individuals, who are the sort of people an economy wants.
"In terms of the donor countries, the problem is that just as we are benefiting from the fact that most migrants tend to be highly committed and skilled individuals, so they are losing those people.
"It is a positive for us but in the donor countries it is more of a concern in the shorter term."