Britain today promised £15 million to tighten border controls in French ports where hundreds of would-be migrants gather in the hope of smuggling themselves into the UK.
The cash will pay for new technology to search vehicles and goods heading for Britain. A pilot of the hi-tech systems will be carried out at Calais before being extended to Boulogne, Dunkirk and the Channel Tunnel terminal at Coquelles.
The offer was made by Prime Minister Gordon Brown during his summit with French President Nicolas Sarkozy in Evian, France. In return, Mr Sarkozy undertook to step up the removal of illegal immigrants to their home countries.
Since the closure of the Red Cross refugee centre at Sangatte in 2002, would-be migrants have been sleeping rough in and around Calais while they make attempts - sometimes on a daily basis - to cross to the UK by hiding on board cross-Channel trains and ferries.
Several hundred migrants, many from Afghanistan and Iraq, are reported to sleep in makeshift tents in an area nicknamed The Jungle outside Calais.
A joint Franco-British declaration issued following the Evian summit states that the situation on the French side of the Channel is "of concern due to the continued migratory pressure resulting from the presence of significant numbers of irregular migrants attempting to reach British territory".
Hailing today's agreement, immigration minister Phil Woolas said: "We have one of the strongest borders in the world, and today's agreement with our French counterparts has made it even more secure.
"An extra £15 million has been invested to pay for new technology as part of a hi-tech pilot in Calais. This will see the latest state-of-the-art technology being used to boost searches of vehicles and goods heading for Britain.
"The UK Border Agency will roll out the latest detection technology to ports in Boulogne, Dunkirk and Coquelles.
"The French Government is determined to return more illegal migrants by stepping up removal flights. The UK recognises this effort and maintains its own commitment to removing foreign nationals with no right to be in the UK.
"Last year we stopped 28,000 individual attempts to cross the Channel and searched one million lorries - these changes will further strengthen the ring of steel that protects Britain."
Speaking in the House of Commons, Home Secretary Alan Johnson said: "The investment will be made on the understanding that the French will, in return, effect significant returns of illegal migrants from northern French regions.
"So it's aimed at first of all securing the route from France into England and secondly ensuring that France sends more immigrants from northern France back. So I think that looks like a balanced agreement."Reuse content