Illegal immigrants are slipping into Britain via the port of Newhaven as part of an international smuggling ring.

In the past three months 12 immigrants have been found huddled inside containers unloaded from the Dieppe ferry.

Customs officers say immigrants are being taught to evade the carbon monoxide testing procedures to detect bodies by being issued with large plastic bags to breathe into during security checks on lorries and other vehicles.

Many are being smuggled in from countries as far afield as the Middle East and Kurdistan.

Three illegal immigrants were found inside containers yesterday morning and one was found on Tuesday.

There is only a token immigration service at Newhaven and a minimum customs and excise facility.

Passengers at Newhaven can make use of an "honesty" phone line which allows them to ring up and declare excess goods they are bringing into the country.

The stowaways have admitted paying up to 7,000 Euros, almost £5,000, for the four-hour crossing on the ferry service operated by Transmanche.

Maurice Longstaff, 59, a partner in Maple Handling, the Newhaven company which has the contract to unload and store the container contents from the quayside, has discovered many of the immigrants.

It is the fifth time this year he has found illegal immigrants inside containers on lorries.

Mr Longstaff said: "The numbers coming through the port are increasing. We have had 12 in the past three months.

"Something is going on in France or even beyond. The whole thing is very organised.

"They are put into the containers in France and someone is locking the doors behind them.

"I then open up the trailers at our premises after they have been collected from the quayside and find eyes glaring at me.

"Sometimes they try and make a run for it. Normally I just shut the doors and phone the police, who do respond quickly and hand them over to immigration.

"I understand Immigration then give them a voucher and put them on a train to travel to the immigration office in Croydon and, of course, they disappear. It makes you wonder who is wandering the streets of Britain."

Last year Mr Longstaff chased five illegal immigrants in his van through Newhaven after they jumped from one of his trailers. They were caught with the help of police. They too were given vouchers to travel to Croydon and disappeared.

Norman Baker, MP for Lewes, said: "If I was a people smuggler I would use Newhaven. It is disgraceful after all the episodes we have had.

"Newhaven is one of the weakest links in the security of this country. I have raised the matter on the floor of the Commons and I shall continue to do so."

Steve Forrest, operations manager for Transmanche Ferries at Newhaven said: "We do have extensive security at Dieppe and use sniffer dogs, but apart from unpacking virtually every item that is loaded on to every container there is nothing we can do. Sometimes we even do this. Many stowaways have been found this way."

A spokeswoman for the Immigration Service said: "We have standard procedures for dealing with illegal immigrants and asylum seekers. There is a centre which deals with asylum seekers at Croydon and sometimes they are given vouchers to travel to the centre to register their claim."