More than 24,000 people from the eight ex-communist states which joined the EU on 1 May had signed up to the UK's workers register by the end of June.
Fears have been expressed over the level of migration from the former Eastern Bloc
Home Office figures show that more than 14,000 of those were already in the UK before enlargement.
In a statement officials said there was "no evidence" that accession workers were exploiting the benefits system.
Home Secretary David Blunkett said there was some indications numbers registering had peaked.
Freedom of travel
He added: "Our transitional arrangements have made it possible for workers from the new EU countries to work here legally and pay taxes.
"These new EU citizens have been able to travel freely across all EU countries since 1 May.
"If we had refused to let them work as other countries have done, we would simply have fuelled the problem of non-tax paying clandestine workers."
A separate set of figures published on Wednesday shows a 25% increase year-on-year in the number of people arriving from ex-Communist states now in the EU.
In May, 99,000 arrivals were recorded by the Office for National Statistics (ONS), a
fifth more than in the same month of 2003.
Of the citizens from the accession states, 240 had tried to claim unemployment benefits and all but six were immediately refused.
Some 102 had claimed homelessness assistance but just 21 were successful and they had all been in the UK before 1 May.
The Home Office said 190 people from the accession states had been awarded child benefit.
Of those registered on the government's work scheme 94% had no dependants.
Mr Blunkett said: "It is likely that those working here will do so for short periods of time before returning home, taking with them the new skills they have acquired and generating economic growth and new opportunities in their own countries."
The ONS figures indicate that people from accession states made up 7% of all May arrivals in the UK from the EU.