Foreign lorry drivers are putting lives at risk by overworking, using vehicles with serious faults and overloading their trucks, a police chief has said.
Around 400 people are killed annually in UK lorry accidents
Association of Chief Police Officers spokesman Ch Supt Geraint Anwyl said EU expansion had made the situation worse.
Penalties against the offending haulage companies were not tough enough because of the huge profits available, he said.
One Polish driver told BBC One's Real Story he drove in the UK despite not understanding any British road signs.
About 400 people a year are killed in accidents involving lorries in the UK. On a typical day there are 12,000 foreign lorries and 95,000 British ones on the country's roads, according to the Department of Transport.
The programme spoke to Jean Dickins, of Hungerford, who was widowed when her husband was killed by a Czech lorry driver going down the wrong side of the road.
The driver was convicted of causing death by dangerous driving but only served half of an 18-month sentence.
"It's not giving out the message that it's not acceptable for these people to come and flout the rules," she said.
Ellen Clarkson's two children Laura, aged 13 and Robert, aged nine, were killed in a pile-up on the M11 in Essex after a collision with a German driver who had been working excessive hours.
She said: "It was totally preventable, my children needn't have died. He knew what he was doing was illegal and as far as I can see he was in a lethal weapon."
Ch Supt Anwyl, of North Wales Police and a spokesman on traffic issues for the Association of Chief Police Officers (ACPO), said: "This is a very serious issue and lives are at risk here.
"As we've seen accession countries coming into the EU, the offending rate is getting greater and greater."
The Polish driver, who did not wish to be named, spoke about the kind of hours foreign drivers were doing.
He said: "Sometimes we would work overtime to get through the load - up to 26 hours.
"My record was 32 hours more or less. I didn't understand the English road signs. I still don't.
"I came to the conclusion that sooner or later I would fall asleep behind the wheel killing somebody or killing myself."
The police and the Vehicle and Operators Service Agency (VOSA), which checks that lorries are safe, said there were serious problems with drivers and lorries from both Britain and abroad, but that those from abroad were statistically more dangerous.
Real Story spent a day with the police at Dover, where most foreign lorries come in from Europe, and a day at Holyhead, one of the main departure points, with inspectors from VOSA.
It found that, out of the 206 vehicles they pulled over, more than a third - 77 vehicles - were taken off the road because they were unsafe.
Rusty brakes about to fall off, arrests for excessive driving hours, vehicles dangerously overloaded and bald tyres about to explode were among the problems discovered.
Dell Evans, a senior manager with VOSA, said that despite extra funding from the government to tackle the problem, the inspectors were still fighting a losing battle.
A Department for Transport spokesman said: "We are determined to tackle those lorries who choose to flout UK law.
"Every day, VOSA officers take unsafe vehicles off our roads and when the Road Safety Bill becomes law they will be granted powers to collect penalties from non-UK drivers at the roadside."
Real Story: Lethal Lorries is broadcast on BBC One at 1930BST on Wednesday 25th October 2006