The Port of Dover has declared a "critical incident" due to huge traffic queues affecting holidaymakers.
The seaport's boss, Doug Bannister, said they have been "badly let down" by "woefully inadequate" and "insufficiently resourced" French border controls in Dover.
Travellers have been warned not to head to the Kent port on what is expected to be one of the busiest days on the roads in the UK as summer holidays start for millions of kids.
