About half of the people who moved to Britain from countries that joined the European Union in 2004 have already left the UK, according to a major report published this week.

The numbers arriving from countries like Poland are falling, and greater numbers than before are leaving, says the report, published by the Institute of Public Policy & Research (ippr). Those migrants that remain in the long term are likely to be the best qualified and most aspirational, it says.

Dr Danny Sriskandarajah, head of migration research at the ippr and report co-author, said: “Our research shows that those who are likely to stay in the UK will move up the career ladder. As they find their feet and improve their English, more Poles will want to pursue their professions than pluck poultry in the future.”

The Insitute of Public Policy & Research (ippr) estimates that since 2004 just over one million migrant workers have come to Britain from the eight Central and Eastern European countries that joined the EU at that time.

Polish nationals, by far the biggest nationality within this group, are now the single largest foreign national group living in the UK.

But the ippr believes that around half of these migrant workers have returned home already - and that many more will follow suit.

The ippr believes fewer people from the new EU member states will come to the UK in the coming months and years, and more of those currently here will return home.