International asylum centres are being debated this week - what are they, and how would they work?
By Dominic Casciani
BBC News Online community affairs reporter
What are the government's proposals on international asylum centres?
For the past year, the government has floated a number of proposals for asylum centres outside of the UK.
It suggested creating 'regional protection zones' which would be in or next to areas witnessing major flows of people. These zones would offer a safe haven to those fleeing persecution but keep them within touch of their home countries.
The second proposal was to create 'transit centres' on the fringes of the European Union which would hold all applicants heading west.
Downing Street suggested these transit centres would handle applications for those seeking to enter the UK.
The list of proposed sites for these centres is thought to have included nations on the major transit routes such as Turkey, Morocco and Somalia.
Where does Europe come in?
Migration experts argue the European Union needs to work closely together on asylum because it's a shared problem. Excluding asylum seekers at one end of the continent may only lead to their arrival at the other, they argue.
The UK Government points towards last year's deal with France to close the Sangatte refugee centre in Calais as a model deal which has benefited both countries, though critics argue it has only redistributed asylum seekers rather than tackling the causes of migration.
Another significant issue which most people agree needs to be addressed across Europe is people smuggling.
Organised crime is heavily involved in trafficking people across the European Union.
Leaders are expected to debate both issues at their summit in Thessalonika, Greece on 20 June.
So what does the United Nations think?
The UN's refugee agency (UNHCR) ultimately has responsibility for refugees around the world. While the EU only takes a tiny proportion of the world's refugees (2% in the UK), it accepts that something needs to be done.
Secondly, the UK's proposals would only work with UN backing because it would probably have to run transit centres.
So far, the UNHCR has opposed the UK's proposals for transit camps outside of the EU, arguing there needs to be a co-ordinated response.
Why does it think they would not work?
It warns British or European transit camps on EU borders, such as Turkey or in Ukraine, could act as magnets - in effect they would become a series of Sangatte camps which would potentially be prey to organised people smugglers and other criminals.
Secondly, the UK's proposal for regional safe havens remains unclear.
The UN runs enormous refugee camps on the borders of major conflict zones.
These provide a place of safety - but persuading the inhabitants that it is safe to return depends on the internal security situation back home.
So what does this leave us with?
The UNHCR says the European system needs to sort out genuine refugees from those more likely to be economic migrants.
It says genuine refugees should still be processed by asylum systems in the countries where they arrive.
Those who are rejected could be handled collectively by the European Union within its own borders, an idea that appears to be gathering momentum.
It thinks the magnet effect would not apply because centres within the EU would be primarily concerned with removal rather than admission.
But the agency says these centres would only work if they had cast-iron procedures to ensure that those who have exhausted their rights are quickly returned to their home countries.
Australia's tough transit centre policy is controversial because asylum seekers can be detained indefinitely in a legal limbo if there is no way they can be sent home.
To a similar but far lesser extent, the expansion of detention in the UK and other EU nations mirrors what is happening in Australia.
So will the UK have these offshore centres or not?
After much speculation, ministers have confirmed they have "no current plans at all" to send asylum seekers to camps outside the EU's borders.
The government has also specifically denied a centre due to open in Croatia would be used to house asylum seekers from the UK.
Immigration minister Beverley Hughes told MPs on 16 June there was "steady progress" towards setting up protection zones - in other words the mood music suggests some kind of European-wide system may be agreed.
What about the wider legal framework?
Jack Straw, the previous home secretary, was the first to suggest that the UK would have to rethink its obligations under the 1951 Geneva Convention, the document which sets out the legal definitions of refugees.
The document was written in the wake of World War II and its critics, including present Home Secretary David Blunkett, say it simply does not reflect the modern shape of migration. The government still says it wants to renegotiate the convention but there has been little movement in that direction.
The second area of international law applying to asylum seekers is the European Convention on Human Rights.
The prime minister and David Blunkett have both suggested the UK may rethink its commitment to the convention.
But critics suggest this would be impossible - not least because one of the major constitutional changes introduced by this government was embedding the convention into British law.