Many of the blocks have been in place since 10pm on Sunday night and are at major road junctions. The traffic problems they are causing are being made worse by instances of flooding in some areas of south-east and south-west France.

Although many hauliers are reported by the UK's Freight Transport Association to be allowing cars through, lorries are being detained.

Talks between union leaders and haulage company operators are continuing, however. An agreement is likely to be reached swiftly between the four smaller unions but the non-signatories are the largest unions, which may continue their action.

Action on the French roads has caused disruption to fresh produce transport in the past, most notably in the late 1990s affecting Spanish exports and some arrivals into the UK.

French farmers and growers successfully blockaded supermarket regional distribution centres last week and their leaders have reached an agreement on supplier relationships.