The numbers speak for themselves. In 1992, 39 people applied for asylum in Ireland. By last year, that figure had grown more than 280-fold

to nearly 11,000. And 14 per cent of those 11,000 asylum-seekers arrived at Rosslare from the French port of Cherbourg. An unknown number also journeyed from French airports.

Alarmed by the explosion in immigration statistics, the Garda Siochana established the National Immigration Bureau in Dublin last May. On November 20th, when the 1996 Refugee Act came into force, gardai began travelling on all Irish Ferries ships to France, vetting passengers as they boarded in Cherbourg.

The reduction in asylum applications at Rosslare was immediate and dramatic - from nearly 200 applications per month to only four in December. From November 20th last to December 31st, on the advice of gardai, Irish Ferries staff refused 124 people permission to board the ferry. A further 39 people were not allowed to disembark from the ferries by immigration officers at Rosslare. Chief Supt Martin Donnellan, the head of the National Immigration Bureau, believes two other measures - the appointment of Insp John Gilligan as liaison officer in Paris on March 1st, and the introduction of carrier liability legislation this summer - will further reduce the flow. Yet no one expects the problem to disappear.

"France is more of a transit point than a destination," explains Ole Bockmann, the Norwegian who heads Irish Ferries in Cherbourg. Most of the immigrants who want to stay in France are French-speaking Arabs and Africans. For others, "the conditions in Ireland are better", Bockmann says. "French Immigration argues that's why so many want to go there. It's easier for them to work for cash in Ireland and Britain."

Commandant Yves Robine, the head of the French Police Aux Frontieres (PAF) in Cherbourg, says stowaways have almost ceased to be a problem since 1998, when the Cherbourg Chamber of Commerce built a fence and installed video cameras around the parking lot where lorries wait to cross to Ireland and Britain.

"Before that, they used to wait until dark, then hide under the trucks or in the roof deflectors. They would cut tarpaulins and hide amid the freight," says Robine.

Robine has uncovered four trafficking networks in the past year when the PAF stopped vehicles carrying illegal immigrants. One was a removals lorry driven by a British couple, carrying 24 Chinese. The drivers were sentenced to 24 and 30 months in French prisons. Another was a camping van driven by a Frenchman of Algerian origin, transporting Sri Lankans. The Sri Lankans had flown from Colombo to Moscow to Kiev. They were then driven across Europe to the Netherlands and on to Cherbourg.

By the time immigrants arrive in Ireland, the traffickers are nowhere to be found. Chief Supt Donnellan arrested a Romanian asylum-seeker who was travelling back and forth between Cherbourg and Rosslare with other Romanians, but freed him for lack of evidence. A German arrested in Larne, Northern Ireland, is now serving a prison sentence after taking nine East Europeans in a camping van from Cherbourg to Rosslare and then north en route to Britain.

Insp Gilligan, who was seconded to Interpol in Lyon for three years before taking up his post in Paris, says immigrant trafficking is one area where international criminals co-operate well.

"The drivers may only earn 800 French francs (£96) per day to get the immigrants to the point of embarkation," he says. "Those at the highest-risk point, the border, are the lowest rung of a trafficking ring. The `untouchables' - the guys making the most money - don't get caught."

Police and ferry companies say that forged travel documents are now the single greatest problem in stemming illegal immigrant traffic between France and Ireland.

"False papers can be made by anyone with a good photocopier," says Bockmann. "The untrained eye can't tell the difference, and the immigrants are very smart about choosing an identity that looks convincing. The Africans get British or Dutch papers; the Romanians obtain Portuguese, Spanish or Italian documents. It's a very sensitive issue. In France, you are not allowed to tell someone: `Sorry, you look suspicious.' "

When the flood of East European immigrants began to arrive in the mid-1990s, they looked like refugees, Bockmann adds.

"Now they look like respectable businessmen," he says. "We even had a group wearing tracksuits and carrying Auchan [supermarket] shopping bags like the ferry crews."

The French border police in Cherbourg arrested and deported 211 immigrants with false documents last year. Nearly 10 times that number were refused permission to board ferries to Ireland, although many of those were legally in France. Commandant Robine has only 30 men to deal with 4,000 passengers a day. When an immigrant is deported, it takes two policemen two days to drive him to Roissy and see him onto the aircraft.

"They're totally overworked, with no overtime," says Gilligan.

There have been allegations that French officers pushed immigrants on to third countries, to rid themselves of the problem. Last September, the French ministry of the interior apologised to Brussels after a van belonging to Police Aux Frontieres dumped 45 Kosovar and Kurdish asylum-seekers across the Belgian border. Yet ferry operators and gardai support Robine when he insists that his orders "are to be firm and vigilant, and not to let people through".

Ill-defined responsibilities are part of the problem. Ferry operators feel an unfair burden is placed on them. If a passenger is refused entry to Ireland or Britain, the company must return him to France free of charge. Carriers already pay a £2,000 sterling fine if they inadvertently transport an immigrant to Britain. A similar fine is expected soon in the Republic.

ASG, a security company hired by the port of Cherbourg, works with the ferry companies to search vehicles with dogs. "It shouldn't be our job to do this," complains a French ferry executive who wishes to remain anonymous. "Border police are meant to control borders, but they don't have enough men."

Indeed, Police Aux Frontieres plans to withdraw its agents from the port of Roscoff in Brittany next summer, leaving the task of intercepting immigrants to customs officers who are trained to look for contraband, not people.

But Robine says searching vehicles is not his job either. "We are responsible for security. Policemen are not paid to do this type of work. Our work is much more in-depth - the proof is that we manage to dismantle networks. That's a more efficient way of working," he says.

The French police officer says it would be against rules for him to express an opinion on how immigrants might best be dealt with. But Bockmann of Irish Ferries feels no such reservations.

"Each state cannot just send them on and wash their hands of the problem," he says. "There has to be a European policy to help them in, for example, Romania, rather than France or Ireland. "The thousands of francs or pounds we spend on each asylum-seeker could be better spent in the countries concerned. Fines [against carriers] won't solve anything. They just make everything more expensive for the normal innocent traveller."