Britain will not take any of the 40,000 migrants due to be relocated from Italy and Greece under the terms of a deal thrashed out at the European Council in Brussels.
Prime Minister David Cameron made clear in a fractious meeting on Thursday night that the UK will not take part in the process which will see asylum-seekers who have crossed the Mediterranean by boat dispersed around Europe over the next two years.
But Britain is expected to receive a total of around 800 Syrian refugees over three years under an existing resettlement scheme for the most vulnerable individuals in camps close to the war-torn country.
The arrivals will form part of more than 1,000 vulnerable people to be taken in by the UK each year after Mr Cameron agreed last week to expand the UK's participation in a UN programme to resettle refugees who have fled from their home countries, including those affected by conflict or civil war.
Disputes over the migrants have dominated a European Council summit at which Mr Cameron also secured agreement to kick off the formal renegotiation process which will pave the way for an in/out referendum on Britain's membership of the European Union by the end of 2017.
Mr Cameron said he was "delighted" by the outcome, but British sources confirmed that there was only brief discussion of the issue during a break in the migration debate over dinner last night.
The Prime Minister, who had spoken directly to all his 27 EU counterparts ahead of the meeting, spoke for only around five minutes, after which Council President Donald Tusk confirmed that talks between UK and EU officials would begin shortly, with national leaders returning to the subject at a summit in December. The only response came from Belgian PM Charles Michel, who said that all EU leaders should be consulted before final proposals are put to the Council - something which the UK has said it intends to do.
The European Council president warned: "One thing should be clear from the very beginning. The fundamental values of the EU are not for sale and so are non-negotiable. We should consider British concerns, but only in a way which will be safe for all Europe."
Mr Cameron's demands for treaty change to cement the reforms he wants received a lukewarm response from fellow leaders, with European Parliament President Martin Schulz saying there was "quite some resistance" to the idea.
Estonian PM Taavi Roivas raised the prospect that the move could trigger a wave of referendums across the continent - any one of which could block changes which must by unanimously agreed by all 28 countries.
"Treaty change would probably need referendums all around the EU and that would cause some difficulties as well," Mr Roivas told the BBC.
British officials confirmed that any changes agreed may not be in place by the time of the referendum in the UK, but played down the prospect that they may be subsequently unpicked during the lengthy ratification process.
Mr Cameron will secure "legally-binding and irreversible" assurances that EU law will be changed to incorporate the reforms, which will be "crystal clear" to voters, said one official.
Mr Roivas also warned the Estonia did not want to see EU citizens' right to free movement - a key UK concern - diluted "even in the smallest way".
Mr Tusk announced that agreement had been reached to relocate 40,000 migrants from Italy and Greece over the next two years to other EU states, while a further 20,000 refugees will be resettled from camps in the Middle East and Africa.
But there was no agreement on mandatory quotas for individual countries, and Britain - with Ireland and Denmark - has the right to decline to take part, under its opt-out from EU home affairs issues.
British sources said the UK was already one of the largest contributors to resettlement schemes for vulnerable refugees, taking in around 1,000 annually - including 187 from Syria in the first year of a three-year scheme.
Last night's debate saw Italy's premier Matteo Renzi pitched against countries including Hungary, Poland and Lithuania which were reluctant to accept mandatory quotas of refugees - many from Syria and Eritrea - who have arrived in Europe after making the perilous Mediterranean crossing from north Africa in ramshackle boats.
Mr Renzi was reported to have accused other EU states of lacking "solidarity", telling them: "If you don't want to take the 40,000 you are not fit to be called Europe."
Lithuanian President Dalia Grybauskaite said she was "not satisfied" with the tone of the debate, but accepted its outcome. "We are ready to help, but we would like also to be treated with respect," she said.
The technical talks which will get under way over the next few weeks between UK and EU officials will seek solutions to British concerns including restricting welfare for EU migrants, an opt-out from the goal of "ever-closer union" in Europe, greater powers for national parliaments and protections for countries - like the UK - which are not members of the single currency.
Speaking as he left the talks at around 2.45am, Mr Cameron said: "I am delighted that the process of British reform and renegotiation and the referendum we are going to hold - that process is now properly under way.
"People always say to me these things aren't possible, we will never get them done. Once again, we have proved we will get them done.
"We have started that process and it's under way."
But Labour accused the Prime Minister of caving in to opposition from other EU states.
Shadow foreign secretary Hilary Benn said: "All year the Prime Minister has been saying that change to the treaty was a definite requirement and yet now, faced with entirely predictable opposition from other member states, he is signalling retreat while pretending that all he ever wanted was a post-dated cheque."