Eastern European immigrants 'overwhelming benefit UK economy' Mr Cameron also said he wanted eventually to restrict the ability of migrants from poorer EU states to move to richer ones, angering the European Commission. The announcement followed mounting fears of a sharp increase in immigration from Bulgaria and Romania when freedom of movement restrictions expire on December 31. "Free movement of people is a cornerstone of EU integration - an indispensable functional building block of a truly integrated Single Market," said the foreign ministers of the so-called Visegrad Four (V4). The ministers said migrants from central and eastern Europe, whose ranks Cameron puts at about a million people, had been hugely beneficial to the British economy. "They are younger and economically more active than the average British workforce; they also contribute to UK national revenues far in excess of the social benefits they use," the ministers said. They added that any abuses of welfare systems should be tackled within the existing EU legal framework. "The V4 countries hope that any measure to be introduced in this context by the United Kingdom, or any other Member State, will be compatible with the legal requirements of the European Union," they said. Hungary says around 300,000 of its nationals work in Britain, and puts its domestic workforce at almost 4 million. Cameron says he shares many Britons' concerns about a possible influx of migrants from Romania and Bulgaria next year, when EU restrictions on the bloc's two poorest countries expire. Bulgarian Foreign Minister Kristian Vigenin has called Cameron's plans discriminatory and appealed to London to acknowledge Bulgaria's contribution to the European Union. Romanian Deputy Labour Minister Codrin Scutaru called Cameron's remarks unacceptable and populist and said Romania demanded and deserved the full rights of an EU member, according to the news agency Mediafax. Additional reporting by Tsvetelia Tsolova in Sofia and Luiza Ilie in Bucharest