The number of foreign workers coming to the UK has almost doubled over the last five years, due primarily to EU expansion, new National Insurance figures reveal.
The figures do not indicate the number of foreign workers in the UK because they do not account for those leaving, but they give some indication of the nature and extent of legal immigration to the country.
Two and a half million people have moved to Britain since 2002, the overwhelming majority of whom are under 35.
New EU countries accounted for nearly half of those arriving last year, with an influx of 321,000 people from central and eastern Europe.
But the figures also explode certain immigration myths, including widespread beliefs that most immigrants abuse Britain's welfare system.
Last year's figures show only 2.4 per cent of immigrants claimed out of work benefits after receiving their National Insurance number.
But the Conservatives claimed the figures still proved the government was taking too soft an approach to immigration.
Shadow work and pensions secretary Chris Grayling said: "At a time when Gordon Brown is refusing to provide a pensions lifeboat for the 125,000 British pensioners who have lost their pensions, I think people will find it surprising, to say the least, that so much money is being spent by our benefits system on people who are supposed to have come to the country to work."
The government rejected that criticism, saying the National Insurance figures corresponded to the Home Office's own data.
A Border and Immigration Agency spokesperson said: "The government is committed to pursuing a balanced migration policy and from 2008 will be rolling out its points based system for managed migration. This will selectively admit skilled migrant workers to the UK as long as it is in the interests of our economy.
"However, there are legitimate concerns about managing some of the effects of migration on communities. We are listening to these concerns," the spokesperson added.
"That is why we have taken a more gradual approach to opening our labour market to people from Bulgaria and Romania by maintaining restrictions and introducing quotas on low skilled jobs."
Despite being ridiculed by business leaders and the government, the Conservatives still propose an annual limit of immigration to the UK, a manifesto pledge they originally made under Michael Howard.
Liberal Democrat home affairs spokesman Nick Clegg adopted a different line to his Conservative counter-part, arguing immigration had a positive impact on the UK's economy.
He criticised the government for failing to prepare sufficiently for the effect of EU expansion, however.
"A liberal open immigration policy only makes sense if you also plan for its consequences," he said.
"It is clear that the government has failed to plan adequately both in terms of housing and funding for local services.
"It should be remembered, however, that people are only coming to Britain because they are successfully providing services and doing jobs available in the British economy to the benefit of British consumers."
Government figures reveal immigrants contribute £2.5 billion to the Treasury every year.