The number of fines jumped from 998 in 2012/13 to 3,319 in 2014/15, according to official figures released to the Press Association under the Freedom of Information Act.
Under Home Office rules, drivers can be hit with civil penalties of up to £4,000 for each migrant found hiding in their vehicles.
Vicky Woodfine, a solicitor at DWF who specialises in road transport law, told City A.M. that she had seen a drastic increase in the size of her case load in the past year, with even more work this summer.
“We have hit the pinnacle,” she said. Woodfine added that she was “baffled” as to why the government is fining hauliers amid the chaos in Calais.
She said: “I would have hoped that they would say we are not going to be issuing any penalties, but it is business as usual.
“They are still expecting hauliers to police those borders themselves,” she added.
Road Haulage Association (RHA) chief executive Richard Burnett called Calais “a complete nightmare” for hauliers.
He continued: “It is impossible for drivers to prevent determined migrants getting into trucks and with 5,000 migrants in the Calais area our drivers are exposed.”
A Home Office spokesperson said that the civil penalty regime is intended “to ensure that all drivers are taking reasonable measures to stop migrants from boarding their lorries”.