ONDON, Feb. 23 — Britain on Monday joined a broad front of nations troubled by fears of unchecked immigration across the former Iron Curtain, announcing new controls on workers from Central Europe whose countries will become members of the European Union on May 1.

The British moves mean that, apart from Ireland, most European Union members have now introduced some restrictions on workers from those countries — a marked reversal of the vaunted openness to outsiders once displayed by such European nations as Sweden and the Netherlands.

In Parliament, David Blunkett, the home secretary, said the government would introduce a requirement for workers from the so-called accession countries to be listed on a register of legal workers.

"Their right to work in the U.K. will depend on their being issued with a registration certificate," he said.

He also said immigrants from the new member states would not be able to draw unemployment, housing and most other benefits until at least 2006. The restrictions are not so severe as those announced by France and Germany. But they represent a reversal — under pressure from opposition leaders and tabloid newspapers — of Prime Minister Tony Blair's earlier promise of unfettered access for the new members of the European Union.

"We welcome people, as we have throughout the centuries, to come to our country to work, to contribute and to be part of our society," Mr. Blunkett said. "We reject those from wherever they come who exploit our hospitality.

"For two years, and possibly longer, we will require accession nationals to be able to support themselves. If they are unable to do so, they will lose any right of residence and will have to return to their own country."

Citizens of the present 15 European Union countries do not face such rules. Mr. Blunkett's office said later that East European immigrants working legally would qualify for some benefits, provided they were paying income taxes. They might also qualify after a year for other payments.

On May 1, the European Union is set to expand from 15 to 25 members. With the exception of Malta and Cyprus, which are not covered by the new regulations, the new members are generally poorer former Communist countries and have far more jobless young people than the present members.

Western European nations like France and Germany, though, have their own unemployment problems and sluggish economies. They have said they will restrict access to their labor markets for up to seven years. In Britain, which has much lower unemployment than most of Europe, the debate has turned on largely emotional fears that tens of thousands of Eastern Europeans will flock to Britain to draw benefits without working for them.

Unemployment in Britain is at a 28-year low of 2.9 percent.