The Port of Dover, Britain's main gateway to Europe, on Friday declared a 'critical incident' over long delays, blaming a lack of French customs officials for causing a bottleneck as holidaymakers left for summer breaks.
Britain's departure from the European Union means passengers bound for France face enhanced checks by French officials.
The port has increased customs booths to accelerate the process but it said on Friday they were under staffed, leading to gridlock in Dover on what is typically one of the busiest periods of travel, when schools break up for summer.
A local French police body said delays had been caused by an "unexpected technical incident" at the Channel Tunnel, without elaborating. The French embassy in London later tweeted that all border checks were operating at full capacity.
Liz Truss, Britain's foreign secretary who is competing to become the next prime minister, said the "awful situation" was unacceptable.
"We need action from France to build up capacity at the border to limit any further disruption for British tourists and to ensure this appalling situation is avoided in future," she said in a statement.
The major delays at the port come as some airports also struggle to recruit enough staff to manage the post-pandemic rebound in travel, leading to chaotic scenes at London airports.
A spokeswoman for the Port of Dover said CEO Doug Bannister had declared the situation a 'critical incident'. They did not specify what it meant in practical terms.
"To be let down in the way that we have is just so frustrating," Bannister said.
Graham Stuart, Britain's minister of state for Europe, told Sky News that the government had been working with France to clear the backlog at the port, which handles 12 million passengers each year.
"We are doing everything we can ... it is not a border force problem as such, it is the French authorities. All we can do is continue to work with them," Stuart said.
Dover and Calais have what is known as juxtaposed border controls, where French authorities check passports on British soil before departure, and vice versa in France.
"Please arrive prepared for a prolonged wait - carry snacks and additional water with you," P&O Ferries, one of the main passenger operators from Dover, said on Twitter.
The operator said its services from Calais were operating smoothly.
(Reporting by Muvija M; Additional reporting by Farouq Suleiman and Juliette Jabkhiro; Writing by William James and Kate Holton; Editing by Christopher Cushing, Kirsten Donovan and Louise Heavens)
