The Government is facing crisis in its attempts to prevent European foreign nationals coming to the UK to claim benefits, Work and Pensions Secretary Iain Duncan Smith said.
He told MPs it is currently too easy for migrants from the European Economic Area to pass a habitual residency test to prove they live here, so entitling them to benefits.
Mr Duncan Smith said the Government tried to make it harder but faced tough opposition from Brussels.
Meanwhile, the Government is looking at ways of forcing councils to detail to whom they are offering social housing, while GPs will be handed strict guidance so they know they can refuse to treat certain migrants who have no right to claim free services on the NHS, the minister said.
Responding to an urgent question from Labour MP Frank Field in the Commons, Mr Duncan Smith said:
Migration campaigners have claimed that as many as 250,000 Romanians and Bulgarians are set to arrive in Britain.
Temporary curbs were imposed on both countries in 2005 to protect the British labour market, but they expire at the end of December and cannot be extended.