The European Commission says the end of restrictions on Romanians and Bulgarians from working across the EU has not so far resulted in plane-loads heading west.
There have been fears particularly in the UK that large numbers would come.
The British government is tightening rules to ban EU immigrants from claiming benefits for three months after arriving in the country.
It has also talked of imposing a cap on European migrants.
The Commission was asked for its response.
“The free movement of workers is a fundamental principle which is established in the treaties, which have been ratified by the parliaments of the 28 member states. Any modification of the treaty requires a negotiation of all member states,” said EU Commission spokesman Jonathan Todd.
The British Prime Minister David Cameron has suggested EU treaties could be changed to ban European migrants from claiming child benefit.
Many in the UK fear a repeat of a decade ago when EU enlargement led to more than a million Eastern Europeans coming to Britain – in albeit different circumstances.
In 2004, Britain was one of only a handful of countries to open its labour markets to eastern countries amid a relative economic boom. The opening of internal EU borders to Bulgarians and Romanians on January 1 this year applies across the European Union.
The issue looks set to dominate the political agenda in the UK in the run-up to European elections in May.