The UK should restrict the right of Bulgarians and Romanians to work in the UK when they join the EU, ex-Labour minister Frank Field has warned.
The UK immigration system is in the midst of a shake-up
He said the UK must "impose barriers" until there was an EU-wide policy.
The UK was one of just three countries in 2004 to give all the new EU citizens - notably from Poland - work rights.
Ministers expected up to 13,000 a year to move to the UK, but 600,000 have so far. A leaked Home Office report warns of pressures on schools and hospitals.
The Home Office document says there is evidence that the influx of foreign workers from the eight ex-communist countries which joined the EU in 2004 - has driven down wages in low-paid jobs.
It warns that ministers may be forced to abandon their refusal to grant council houses and welfare benefits to new arrivals who do not work, boosting the "pull factor" attracting further immigrants.
Government departments have been told to draw up emergency plans to deal with pressure on public services from an expected "step change" in immigration levels when Romania and Bulgaria join the EU next year.
The document, entitled Migration from Eastern Europe: Impact on Public Services and Community Cohesion, was written by junior Home Office Minister Joan Ryan and leaked to the Mail on Sunday.
Mr Field, a social services minister in 1997-8, told BBC Radio 4's the World at One: "In 2004 we could have agreed, like the vast majority of the rest of the European Union, that whereas the community was extended at this point in time, we were not having an open door policy.
"We foolishly went ahead and had an open-door policy and instead of between 5,000 and 13,000 people arriving, in the first year something like half a million did.
"We've now got Bulgaria and Romania coming down the road at us. We need to impose those barriers until there is a Europe-wide policy."
Extra funding needed
In the leaked report, Ms Ryan argues that many more English teachers will be needed to deal with a big rise in the number of eastern European children unable to speak the language.
Hospital beds are being "blocked" by east European patients because they cannot claim social care and benefits if they leave.
And towns and cities where large numbers of new immigrants have settled are now calling for millions of pounds of extra funding to cope, the report says.
The report, which is marked "restricted" and dated 19 July, came the day after Ms Ryan put out another document saying that 45,000 "undesirable" criminal migrants from Romania and Bulgaria could settle in the UK next year.
The document says: "All departments have been asked to consider contingency plans ... in case of a further step change in the number of new migrants."
The UK government has yet to decide whether it will give Romanians and Bulgarians the right to work in the UK when they join the EU.
A Home Office spokesman said: "The new plans for immigration and the Immigration and Nationality Directorate set out by the home secretary last week take into account the increase in immigration in recent years."