Lorry drivers face fines running into the millions - as the numbers penalised for carrying illegal immigrants soars.
Truckers caught carrying the stowaways into the UK have seen their penalties more than triple since 2012.
Home Office figures show more than 3,300 fines were issued in 2014/15 - that's an increase of more than 50% on the previous year.
Over the last three years, around 6,500 stowaways have been found.
With fines as high as £2,000 per migrant - levied against the driver and their employer - the total bill for UK haulage firms can run into millions.
Hauliers says the system is unfair, but the government claims firms' security measures are not robust enough.
Thousands of migrants have attempted to get to the Eurotunnel and nine have died since June.
Around 5,000 migrants from countries including Syria, Libya and Eritrea are now believed to be camped in and around Calais.
The Freight Transport Association said the figures revealed the growing determination of immigrants to smuggle themselves on board vehicles heading to the UK.
Donald Armour, manager of the international department at the FTA, said: "The problem has definitely increased in recent years and you've got huge numbers of people making a real effort to come across.
"Whereas they used to come in ones or twos, you're now often finding 10 to 20 people smuggling themselves on board at any one time.
"The public ask why drivers don't secure their vehicles better but many go to great lengths to stop this happening.
"You find immigrants getting in through the roof, slashing the canvas sides of lorries or jimmying off locks.
"When you're facing that kind of determination, there is only so much you can do and the only real solution is better control of the immigration situation."
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