The countries' accession will be an opportunity, says the IPPR

The Institute for Public Policy and Research said they should get the same full working rights as eight other Eastern European nations got in 2004.

It estimated 41,000 Romanian and 15,000 Bulgarian workers would arrive in 2007.

But campaign group Migrationwatch criticised the figures as a "back-of-the-envelope calculation".

The two countries could join the EU from 1 January next year, but a definite date has not been set. Both countries are confronting issues such as people trafficking, to avoid possible delays.

Underestimated

Official figures have shown the government greatly under-estimated how many Eastern Europeans would come to the UK under the previous expansion.

Research suggested up to 13,000 people would arrive annually, but more than 345,000 signed up to a work registration scheme from 1 May 2004 to the end of 2005.

The IPPR said its 56,000 figure was based on what actually happened after the EU expansion in 2004 and not on the initial projections.

It said numbers of arrivals were likely to be relatively small and their impact on the labour market would be positive.

About 13,000 Romanians and Bulgarians are already in the UK, according to a 2001 census.

'No threat'

IPPR associate director Danny Sriskandarajah said: "Romanian and Bulgarian accession should be seen as an opportunity not a threat.

"Workers from these countries will join an increasingly important Eastern European workforce currently doing hard-to-fill jobs in key sectors and regions."

He added that if it was like the last EU expansion, many people would get "very worked up about migration from Romania and Bulgaria".

"But just as last time, we are likely to see turnstiles not floodgates as young and hard-working people come to the UK to work, save, learn English and go home," he said.

Although Romania and Bulgaria are poorer than the countries which joined in 2004, most workers would go to Italy, Greece and Spain because they are closer and have higher numbers of people from both countries already resident, the report said.

'Risk'

However, Migrationwatch Chairman Sir Andrew Green attacked the IPPR's figures and said they assumed the situation would be similar to the "last batch of Eastern European countries".

"But these countries are much poorer than the previous group so the number of immigrants could be significantly greater.

"It is, therefore, very important that the British government should not again get out of step with the rest of the EU by opening our labour market before others do.

"With unemployment in Britain beginning to rise that is not a risk worth taking."

The campaign group went on to accuse the government of relying on "entirely worthless" figures about the economic benefits of immigration.

It said the Home Office was wrong to say immigrants contributed �2.5bn more in taxes for 1999-2000 than they received in benefits and state services and that the true figure was actually a deficit of �200m.

Migrationwatch claimed it was a flaw in the original sum to consider all children of British and non-British households as part of the "native economy".