More than 3,300 fines were issued by UK Border Force staff in 2014-15, up from 2,177 in 2013-14, the BBC has learned.
The fines can be as much £2,000 per migrant and can be levied against both drivers and their employers.
Hauliers say the system is "unfair" but the Home Office said many lorries did not have "basic standards of security".
The fines, known as civil penalties, can be imposed as lorries enter the UK, and also when they are searched by UK officials at ports in France - such as Calais - and Belgium, under the so-called juxtaposed controls system.
The figures come amid the crisis around Calais, during which thousands of migrants haveUK-bound lorries.
Lawyers acting for drivers and road haulage companies say the way the fines system is being operated is "unfair" given the dangers their clients face.
Joanne Witheford, a specialist road transport lawyer, told the BBC: "We asked UK Border Force if there was going to be any leniency shown to drivers in the present situation.