Outlining his immigration plans, David Cameron has said: "Under the previous government immigration was far too high and the system was badly out of control. Net migration needs to come down radically from hundreds of thousands a year to just tens of thousands."
He added: "As we bring net migration down, so we must also make sure that Britain continues to benefit from it...
"That means ensuring the people who do come here are the brightest and the best, the people we really need with the skills and entrepreneurial talent to help create the British jobs and growth that will help us to win in the global race."
Jonathan Portes, director of the National Institute for Economic and Social Research, said immigrants were "significantly less likely" to claim benefits than people born in the UK - and that those coming from EU countries put more into the economy than they took out.
He told the BBC Radio 4 Today programme arrivals were mostly younger people whereas the bulk of spending went on healthcare and pensions for older people.
"All the evidence suggests that people who come here from within the European Union make a substantial net contribution to the public finances - they pay in far more than they take out," he said.
He also played down the impact of health tourism as a "minuscule" part of a wider funding issue.