European Union ministers meeting in Luxembourg have approved a new five-year framework aimed at co-ordinating policies on asylum and immigration.
The UK put pressure on France to curb cross-Channel migration
They have agreed that decisions on such issues will be taken by majority voting - so the 25 EU states will no longer have the power to veto proposals.
But Britain retains the right not to implement decisions it opposes.
Prime Minister Tony Blair insisted that the UK was "getting the best of both worlds" with the asylum plan.
Britain does not accept proposals for a joint EU border guard or centralised visa processing.
Denmark and Ireland have also negotiated a right to opt out of decisions they do not like.
The EU plan, known as the Hague Programme, is due to be formally approved at an EU summit in Brussels on 5 November.
EU HAGUE PROGRAMME
Five-year plan to coordinate policies on asylum, immigration and cross-border security
EU leaders due to approve it on 5 November
Unanimity no longer required - decisions can be carried by majority voting
Britain, Denmark and Ireland can opt out of EU decisions they do not like
It includes a plan for common deportation procedures and for spreading those granted refugee status more evenly across the EU.
While some countries want to set a deadline of 2010 for agreement on common immigration and asylum rules others say that is too soon.
Under the qualified majority voting (QMV) scheme larger states like Britain are expected to have more power than the smaller EU states.
Britain, which is not part of the EU's common immigration area - the Schengen area - will retain an "opt-in" right, allowing it to ignore any measures it disagrees with.
"We are not obliged to have any of the European rules here. But where we
decide in a particular area, for example to halt the trafficking in people... it allows us to opt in and take part in these measures," Mr Blair said.
The Luxembourg meeting will also cover plans to boost co-operation against terrorism.
UK in vanguard
Explaining why the UK government was backing the QMV system, Home Secretary David Blunkett said "it was agreed ... as a logical outcome of the accession of the new countries, that with 25 nations, you simply can't retain a veto over everything".
"We need the rest of Europe to get its act together," he told BBC Radio 4's Today programme.
"I'm very keen indeed to collaborate with a sensible reinforcement of land
and sea borders.
"We have already helped the Italians and Spanish and Greeks in terms of
putting frigates in the Mediterranean. We are prepared to help with the borders
of eastern and central Europe. We are not prepared to have a border control
agency run from Brussels."
A UK Home Office spokeswoman said the UK wanted QMV because "we are one of the fastest-moving countries on immigration and asylum, and it means we can drive it forward, rather than go at the pace of the slowest-moving member of the EU".