Professor John Salt, from University College London, said that the foreign population in Britain will not shrink during the recession.
He said the country had experienced similar conditions in the 1960s and 1970s, when high levels of immigration were initially halted by an economic downturn.
He said: “If the pattern of the past is repeated then immigration into the UK might well decline rather less than a lot of people anticipate.”
A report he co-authored for the Policy Network, a centre-left think tank, concluded: “The evidence we have been able to gather on past recessions in the UK and more widely in western Europe indicates that foreign immigration falls while unemployment is increasing but only for a limited period.”
In 2004, Prof Salt was commissioned by the Home Office to draw up estimates of the number of illegal immigrants living in Britain, and produced a figure of 450,000 to 500,000.
His latest warning came as Phil Woolas, the immigration minister, announced he is considering adding an ethical aspect to the new points based system to help reduce the impact of the UK draining away top workers from other countries.
Skilled migrant workers will find it easier to come through the new system if they pledge to invest “human capital” in their own country.
He said he could not “morally justify” the toll placed on third world countries when workers such as doctors move to Britain.
He said: “We apply a fundamentally different policy to the developing world than we do to the EU countries. We say to the developing world, ‘Here’s some finance, here’s some trade, but we will take your skilled people.’ Therefore the dilemma of the governments of the developing world is to say to us, as they do persistently, ‘Why are you taking our skills off us?”‘