Tony Blair and key ministers say they have agreed a package governing access to UK jobs and benefits for people from the new EU member states.
UK is not imposing restrictions on new EU member states
MPs will be given the full details - which were agreed during talks in No 10 - on Monday, Downing Street said.
Britain is one of only two existing EU countries to allow people from states like Lithuania, the Czech Republic and Poland the right to work from 1 May.
Moves could include a work permit scheme, and restrictions on benefits.
Tuesday's talks involved Home Secretary David Blunkett, Foreign Secretary Jack Straw and Work Secretary Andrew Smith.
Ireland is the only other EU country to have decided not to place restrictions on the citizens of new member states working.
The government had already indicated it was looking at ways to stop "benefit shoppers" - people turning up and trying to tap into the UK's health and benefits systems.
But there has been support from ministers for allowing the right to work.
Later, Work and Pensions Minister Andrew Smith refused to reveal the details of the package, saying Parliament should be told first.
He denied there had been "panic" over the issue, saying the government had always realised there would need to be regulations after EU enlargement.
"As the prime minister said in the House of Commons, of course there have been the developments in terms of the decisions which other countries have taken," Mr Smith told reporters.
"Anyone sensible would take account of the position in the light of those and that is what we are doing."
The Tories last week accused the government of being confused on this issue.
This came after Mr Blair first indicated Britain was looking at tighter controls to limit migration from Eastern Europe, and then Mr Blunkett insisted there would not be measures to discourage people from heading to the UK to work.
However he told the BBC steps would be announced "shortly" to stop the UK becoming a magnet for people who want to claim benefits and not work.
Conservative home affairs spokesman David Davis questioned why the government had been forced to hold a "crisis summit" nine weeks ahead of the accession date when EU enlargement had been "planned for years".
He said: "Emergency meetings in Downing Street only nine weeks before the accession
date shows what mess they are in."
NEW EU MEMBERS (FROM 1 MAY)
For the Lib Dems, Mark Oaten said: "Blair's victory over David Blunkett surely signals the final victory for populism over principle."
Ex-home office minister John Denham said there were good reasons to allow new EU citizens to work in Britain - for example to fill existing gaps in the labour market.
But he added there was a danger that if a small number of people were perceived to be exploiting the benefits system it could cause "a great deal of trouble".
John Monks, now head of the European-wide version of the TUC, accused sections of the media of talking up the danger that the UK would be "swamped".
Scotland's First Minister Jack McConnell said his country was facing a "serious population problem" with numbers due to fall below five million by 2009.
It was therefore important that the new EU had as "free an economic market as possible because that's the way to global prosperity not just for mainland Europe but for the UK as well".
All existing member states are able to impose transitional restrictions form up to seven years on the right of residents of eight of the ten new EU member states to work and claim benefits.
The idea is that by the end of that period of time the economies of the new members will have grown, thus making it less likely that mass migration will follow.
The restrictions only cover the former comunist states joining the EU - a separate deal means that there are no restrictions on citizens of Cyprus and Malta.