The big question: How do we tackle the crisis over migrants desperate to reach Europe?

Why are we asking this question now?

Europe faces a crisis on its southern shores as desperate Africans crowd into flimsy ships in search of a better life in the rich continent to their north. Malta has been pitched into the front line of the battle against illegal immigration with soaring numbers trying to make the perilous 200-mile crossing from Libya to the Mediterranean island.

Many migrants will hope that if they can make it to Malta, they will then be free to start a new life anywhere in the European Union. But the dreams of many turn to disappointment and sometimes tragedy.

Malta is struggling to cope with the human tide, with nearly 200 illegal immigrants arriving in the past week alone. It is refusing to accept any more newcomers, leaving boatloads of Africans in a diplomatic limbo. They include a group of 26 stranded on a Spanish tug-boat and another boatload eventually that was rescued by the Italian navy after clinging for several days to a vast tuna net. At least their lives were saved.

Eight days ago an aircraft photographed a tiny boat packed with 53 Eritreans taking in water near Malta. It had vanished by the time rescuers arrived.

Which parts of Europe are under the greatest pressure?

The pressure points have changed over recent years. When the Balkans were in turmoil, large numbers fled across the Adriatic. By the turn of the century, Iranians, Iraqis and Afghans were squeezing into lorries that brought them to the West.

Now it's the seas around southern Europe that are the focus of desperate activity, with more than 31,000 migrants landing on the Spanish-owned Canary islands off the west African coast last year - six times as many as in 2005. Bizarre pictures of the emaciated new arrivals collapsing on beaches full of Western tourists symbolised the meeting of the two worlds. Almost all had been packed into wooden fishing boats that began their journey in west African nations such as Senegal or Mauritania some 10 days earlier.

The authorities had been encouraged by a fall in the numbers heading for the Canaries this year. But at least 800 took advantage of warm weather and calm seas to land in a five-day period earlier this month. Ceuta and Melilla, Spanish enclaves in North Africa, inevitably also act as a magnet to young men, who often cross the Sahara to reach them. Huge fences have been erected around them and patrols set up to catch entrants.

The Italian island of Lampedusa, closer to Tunisia than it is to mainland Italy, has also been targeted by a constant flow of migrants.

What is driving Africans to take this desperate step?

The decades-old phenomenon of "wetbackers" crossing the Rio Grande from Mexico for a better life in the United States is a continuing reminder of the pressures that build up when nations with hugely varying standards of living are cheek by jowl. In the same way the income from even the most menial jobs in Europe is in stark contrast to the crushing poverty of such nations as Senegal, Guinea or Eritrea. And it appears that the disparity can only be widened by the growing population and desertification of sub-Saharan Africa.

Instability across much of the continent - notably in the Horn of Africa - is also fuelling mass migration. More Eritreans are currently claiming refuge status in Britain than any other national group.

What happens to migrants if they arrive safely?

In the short term, they are likely enter a netherworld of detention camps surrounded by barbed wire while the authorities deliberate over their future. Some are deported, although removing them to their home countries can be difficult if they arrive without documents and vague over where they came from. Some on Spanish or Italian islands will be transfered to the mainland, where they will hope eventually to be released by authorities powerless to deport them or detain them long.

The likelihood is that they will join the vast army of illegal workers fuelling their nation's economy but barred from using its services. Some may try to head north to France, Germany or Britain, but the chances are that they will remain hidden from official view in their new homes.

Both Italy and Spain have had amnesties for illegal immigrants in an effort to regularise their status, although such a step is always politically difficult.

The authorities in Malta now face an acute dilemma with any illegal immigrants who manage to land - and no mainland to send them to. It has in the past taken a liberal approach to them, but has recently declared that it is full and unable to accommodate any more.

What is the EU doing to stem the flow?

The issue is one of the most acute problems facing most European governments - and one that nations in the front line are struggling to cope with on their own. They should be backed up by Frontex, the EU's borders agency, which has 20 aeroplanes, 30 helicopters and more than 100 vessels at its disposal. But its help has been patchy, and plans for a rapid-response team have yet to materialise. In fact, Spain has blamed the absence of Frontex craft as the main reason for this month's unexpected influx of migrants into the Canaries.

What more positive steps are being suggested?

In an effort to dissuade would-be migrants from leaving Africa, the European Union has allocated €40m (£27m) to boost job creation in the continent of Africa, although it is hard to see how much difference spending on that relatively modest level would make. The EU's Justice commissioner, Franco Frattini, has also proposed setting up "Migration Support Teams" to help African countries get a grip on mgiration. And he suggested the creation of "European Job Mobility Portals" in African countries, which would provide information about job opportunities in Europe.

He has also mooted the establishment of a system of selective immigration to the EU modelled on the US green card system, designed to tackle skills and labour shortages. But the plan has run into resistance from EU states. They argue that such decisions should be taken from national capitals, not Brussels.

How is Britain combating illegal immigration?

Like many EU governments, it is taking an increasingly tough approach to the issue. Any prospect of an amnesty for illegals already here has been firmly ruled out. Border checks have been tightened considerably since 2001 when the Home Office was rocked by pictures of illegal migrants massing at the Sangatte camp, near Calais, ready to make a final bid to reach Britain. At the same time it is introducing new rules that exlude virtually all non-EU lower-skilled workers from coming legally to Britain.

Liam Byrne, the Immigration minister, has warned that uncontrolled immigration risked damaging poor communities and put pressure on schools and housing. Immigrant groups fear that the moves could trigger a new "bidding war" between the main political parties over who can sound toughest on migration.

Although the pictures from Malta or the Canaries seem remote from this country, ministers in this country are aware that the images can arouse the more xenophobic elements of the public. That is why when John Reid, and whoever succeeds him next month as Home Secretary, meets his European counterparts to discuss immigration there is little chance that they will be examining ways of easing border controls.

So should Europe be turning arrivals from Africa back?

Yes...

* Much of southern Europe is densely populated and cannot accommodate large numbers of new arrivals

* Further influxes of of migrants could create resentment among the indigenous population and harm community relations

* Allowing more to enter only creates a "pull factor" encouraging more to follow in their tracks

No...

* Tightening border controls could lead to more tragedies as boats are turned back or take more circuitous routes to reach Europe

* Europe's ageing population increasingly needs a pool of migrant labour to guarantee economic growth

* Why not take advantage of the single-mindedness that often leads migrants to undertake such hazardous journeys?