The association says truckers are threatening to take drastic action unless the government backs down on proposals that could see lorry drivers pay thousands of pounds in fines if they unknowingly carry illegal immigrants into the country.

The warning comes ahead of a meeting between the RHA, led by former Tory transport minister Steven Norris, and immigration minister Mike O'Brien on Wednesday.

Drivers may disrupt traffic at ports

Other possible action open to hauliers in their campaign against the government's proposals include disrupting traffic at ports by insisting that customs officials search every lorry coming into the country for illegal immigrants.

Truckers fears over stowaways was first aroused when the government told a recent the Commons Home Affairs Select Committee that it was considering extending to hauliers the carriers' liability for stowaways which already covers airlines.

This could mean that drivers will face fines of up to £2,000 for every illegal immigrants found in their trucks.

According to the RHA, hauliers who voluntarily report stowaways will still face the same penalties as those who choose not to.

RHA spokesman Dan Hodges said: "Anyone with an ounce of common sense can see that fining drivers who report stowaways is not the way to encourage their co-operation with the immigration authorities.