Many Polish migrants to the UK have returned home
Many economic migrants from central and eastern Europe who came to work in the UK are returning home because of the recession, a report suggests.
The global Migration Policy Institute (MPI) study, commissioned by the BBC, says EU expansion led to 1.4m east Europeans moving to the UK up to 2008.
But the recession in Britain and modest economic growth in Poland have led to a change in this pattern, it found.
The MPI report suggests about half of those migrants have now left.
The report explained in graphics
It also says that migration from Poland in particular is now temporary and circular in nature, with people constantly coming and going.
The weak local currencies had previously made the UK an attractive destination.
However, if the UK's economy picks up, the flow of migrants could change again, the report says.
Recent figures from the the Office for National Statistics suggested that 118,000 more people arrived in the UK than left in 2008 - the lowest level since EU enlargement.
Sir Andrew Green of Migrationwatch said migrants from the A8 countries were "only a small part of the picture which, at least for the time being, is getting smaller". The A8 countries are the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia and Slovenia, who all joined the EU in 2004.
Sir Andrew said: "Only one in seven foreign born workers in the UK is from the A8, according to the Labour Market Statistics from August 2009."
Furthermore, in the calendar year 2007, the last available, only one in four net migrants was from the A8.
"The more recent International Passenger Survey for quarter four in 2008 had only one in 14 net arrivals from the A8."
The report also says there were about 618,000 unauthorized migrants estimated to be in the UK in 2007.
And between 1995 and 2008, the number of non-UK nationals living in the country more than doubled, from 1,948,000 to 4,196,000, along with the number of foreign workers up from 862,000 to 2,283,000.
The report also says Europeans account for half of the UK foreign workforce, and that the numbers of A8 Europeans in the labour force have grown rapidly, reaching just under half a million, or 21.8%, of all foreign workers in 2008.
There were 358,000 Polish workers in 2008, up from 151,000 two years earlier. Polish workers accounted for 15.7% of all UK foreign workers in 2008.
Worldwide, the MPI study says there has been a dramatic global decline in the number of people going to work abroad since the start of the global downturn.
There was a large decline in the number of Mexicans moving to the United States, for example.
It also suggested that the level of remittances - money sent by migrants to family members back home - has declined.