Hauliers have been urged to avoid travelling to Kent ports as the closure of the France-UK border is expected to trigger "significant disruption".
Transport Secretary Grant Shapps' warning came after Dover's ferry terminal closed to "all accompanied traffic leaving the UK" after France moved to impose an inbound travel ban.
The French Government joined a number of other European nations in banning inbound flights from the UK in a bid to prevent the spread of a coronavirus mutation sweeping through London and the south east of England.
Part of the coastbound M20 is being used to stack lorries due to cross channel travel restrictions, with Operation Stack activated between junctions 8 for Maidstone East and junction 11 for Westenhanger.