Labour to force Syria refugees vote in Commons
Labour is promising to force a House of Commons vote on the UK joining a United Nations scheme to accept refugees from the civil war in Syria.
David Cameron said the government would take in the most vulnerable, but queried the need for a "quota system".
The UK would "play the right role", the prime minister insisted.
But Labour said this was not enough to respond to MPs' concerns and announced the party would stage a debate and vote next Wednesday.
The UNHCR - the United Nations refugee agency - is appealing for Western countries to accept 30,000 of those trapped in the region around Syria.
Speaking at Prime Minister's Questions, Mr Cameron said the UK had taken in more than 1,000 Syrian asylum seekers and was fulfilling its "moral obligations to the people of Syria".
He said: "We are also making sure where we can help very vulnerable children who are ill - including a child in a British hospital today - we take action there as well.
"I don't believe you can solve a refugee crisis of this scale when you have got almost half of the nine million population of Syria either displaced or at risk of displacement with a quota system where countries are taking a few hundred refugees.
"But I do agree if there are very difficult cases of people who don't belong in refugee camps who have either been disabled by these attacks, or in very difficult circumstances, I'm happy for us to look at that argument.
"Britain always plays the right role in these desperate humanitarian crises."
Mr Cameron warned that countries which had signed up to the UNHCR scheme, such as Finland, France and Sweden, should not feel that by taking a few hundred people they had fulfilled their obligations.
A senior Downing Street source later suggested the kind of "hardship cases" where the UK could consider taking in refugees might include children who had been orphaned by the war or who had medical needs or mental health problems which could not be dealt with in the camps.
In the Commons, Labour leader Ed Miliband said: "We are not talking about either providing aid or taking vulnerable refugees. We are talking about doing both.
"Given your reasonable tone, will you now open discussions with the United Nations about Britain making its contribution to this programme? All sides of this House want this to happen."
A Labour source later said the party would force the issue to a vote next Wednesday, and hoped to receive the support of MPs from all sides of the House.