The three European Union countries that gave unrestricted access to central and eastern Europeans after enlargement last year have filled vital skills shortages thanks to immigrants, a study says.

Britain, Ireland and Sweden have benefited from recruits who took "hard-to-fill jobs" in healthcare, farming and tourism, according to the European Citizen Action Service, a lobby group chaired by Mario Monti, the former EU competition commissioner.

About 175,000 workers from the former communist countries went to the UK, which has among the lowest unemployment rates in the EU. Ireland took in 85,000, while Sweden is estimated to have accepted about 22,000.

The report also shows that France, which feared being over-run by a wave of Polish workers, issued only 1,600 work permits to Poles in the first 11 months after enlargement, although many more are thought to be working illegally.

Fears over the "Polish plumber" taking jobs in France, which has unemployment of nearly 10 per cent, contributed to the French defeat of the European constitution in a referendum in May.

Twelve "old" EU countries imposed various last-minute restrictions on the entry of new workers before enlargement in May 2004. They did so amid concerns that some newcomers could seek to latch on unfairly to social security benefits; citizens also feared low-wage recruits flooding their labour markets.

The bulk of the immigrant workers to the old EU have come from Poland, whereas Slovenes and Czechs were least likely to move, according to the report, which is based on statistics from national governments and academic research.

Poles made up more than half the new EU workers in the UK, while many also went to Germany, Italy, the Netherlands and Ireland.

So many Poles are working in the UK that Polish political parties have begun campaigning for votes there for the elections later this year.

EU member states will decide in May whether to end the various restrictions they agreed on the new workers or renew the curbs for another three years.

The restrictions were allowed under accession treaties agreed with each of the new members from central and eastern Europe, where wages are considerably lower than in western Europe.

No curbs were put on workers from Cyprus and Malta, which joined the Union at the same time.

Opponents of the restrictions say the EU, with its ageing population, needs more flexible access to labour and the economic dynamism that migrants can help generate.

The hastily imposed curbs caused surprise and anger in the new EU capitals last year and the eight member states have begun a lobbying campaign to overturn the restrictions.