British Prime Minister David Cameron on Wednesday announced a tightening of migrant benefit rules due to concerns over migration levels from Bulgaria and Romania when restrictions are lifted on January 1.
Writing in the Financial Times, Cameron accused the former Labour government of making a "monumental mistake" in allowing Poland and nine other countries access to the UK labour market when they joined the European Union in 2004.
Under his plans, migrants will not receive out-of-work benefits for the first three months in the country and payments will be stopped after six months unless there is a "genuine" chance of them getting a job.
"We are changing the rules so that no one can come to this country and expect to get out-of-work benefits immediately," he told the newspaper.
Some 50,000 Bulgarians and Romanians are set to arrive in Britain in each of the next five years when restrictions are removed, according to research group MigrationWatch UK.
The Bulgarian Ambassador in Britain believes the figure will be much lower, predicting around 8,000 arrivals per year.