French rail and check-in staff protesting over pay and conditions caused long delays when they sealed off entry lanes to Eurotunnel's Calais departure terminal with privatecars.
More than 3,000 cars and 200 coaches, mainly British families returning from a weekend break on the Continent, were stranded for almost eight hours.
The strikers sealed off access by driving about a dozen of their own cars across toll booth lanes at Coquelles, near Calais. In bad-tempered scenes, some determined British drivers managed to break the blockade by pushing through an alternative entry-point to the check-in area.
At one point, two buses and a handful of cars forced their way through the barricades, prompting altercations between workers and waiting motorists. One man was taken to hospital in Calais.
The blockade started shortly after 9am yesterday and was in place for about five hours before the first handful of cars was allowed to board a limited service to Dover on the cross-Channel rail link.
Eurotunnel said clearing the backlog of passengers through a reduced check-in and a partial Le Shuttle service added another three or four hours to the journey times of those held up by the blockade.
With queues stretching at least 4km on to motorways, tired families had to endure another few hours creeping towards Calais; some took about eight hours to get through.
Travellers hoping to find assistance from French authorities were told the problem was of their own making.
A spokesman for the Calais border police said: "Although the problems have arisen from an internal dispute at Eurotunnel, the traffic jams are being made worse by the fact that British passengers are choosing to stay in the road queues rather than finding alternative ways home.
"They fear the ferries are all booked up and are determined to stick it out in the queues until things are moving again."
At the Cheriton Eurotunnel terminal near Folkestone in Kent, hundreds of travellers to France were delayed because fewer Le Shuttle trains were running.
Problems in France were compounded because ferries and hovercraft, alternative cross-Channel routes, were heavily booked over the bank holiday.
Meanwhile, motoring organisations said British roads were "quieter than usual", with damp and cool weather given as the reason for lighter May bank holiday traffic.