More than 80 asylum seekers burst out of a Channel tunnel train at a freight yard near Folkestone in the most serious breach of tunnel security to date.
Police captured 53 of the stowaways in and around the Dollands Moor yard but at least 30 escaped after scaling a fence and crossing the nearby M20 motorway.
The refugees are thought to have boarded the train at its starting point in Milan. Freight operator EWS yesterday expressed fury that the French rail company SNCF failed to find them, despite searching the train in Calais.
SNCF, which is responsible for freight security in Calais, had attached security seals to containers after declaring them free of people.
An EWS spokesman said: "These people should all have been detected by the French authorities but they weren't. We were promised proper security. Tags were attached to these wagons to say that they'd been searched."
British Transport police said the asylum seekers were from Afghanistan and Iraq. There was "evidence of concealment and lengthy habitation" in the wagons, suggesting the stowaways clambered on at the train's starting point in Milan.
Kent police and military police joined the search after security guards at Dollands Moor raised the alarm on Monday night. Police arrested 19 asylum seekers in the yard, and 34 more on the M20. Many were in containers with canvas coverings, which had been cut open with knives. EWS said a container with an SNCF security seal was opened by its staff at Dollands Moor, who found five refugees still inside.
SNCF declined to comment yesterday. EWS's chief executive, Philip Mengel, blamed the British government for failing to put pressure on the French to provide adequate searches of trains in Calais. Some freight operators have suggested that the French government had withheld resources from state-owned SNCF to highlight Britain's refusal to bring its asylum laws in line with the continent. Mr Mengel said: "The UK government is overseeing the systematic collapse of the international rail freight business as a direct result of the actions of the French government."
SNCF is losing £500,000 a week due to the asylum crisis. A total of 22 British freight companies have lost more than £15m since asylum seekers began disrupting Channel tunnel goods trains in November.
Mr Mengel said a "significant trading corridor" was on the verge of closure as a result of the crisis, which has restricted daily freight traffic through the tunnel from 20 trains each way to six or seven.
He said: "The UK government, the French government and the European commission must act to solve this issue. Their collective urgent action is required."
Conservative home affairs spokesman Nick Hawkins said the government should reinstate a bilateral agreement allowing Britain to send any asylum seekers back to France.
Mr Hawkins said the refugees were "economic migrants" rather than people fleeing political oppression. "We are our own worst enemy by letting the message get through that they can just get here and disappear because our regime is so lax."