Travelers waiting in line at the Port of Calais experienced delays of up to six hours.
The lengthy lines at the UK border controls on Saturday have been apologized for by the ferry companies DFDS and P&O Ferries.
DFDS said queues in Calais have been down to about 45 minutes on Sunday.
A spokesperson told BBC News: “Calais was affected by ‘the perfect storm’ of summer volumes in combination with post-Brexit border checks, causing six hours of queuing.
“We worked together with partners to reduce the queues as quickly as we could.”
Speaking to BBC News, she said: “It was little to do with the amount of people but with the poor layout and no traffic control.
“We were traveling back from Belgium and expected to be delayed, so arrived early.
“There weren’t many cars but an hour later we had moved just two cars. The way this terminal is designed is the problem.”
Passenger Josh Williams added he was also stuck waiting in Calais for five hours on Saturday to get a ferry back to the UK.
He shared pictures of long lines of cars filled with families trying to get back to Dover ahead of the new school year starting for many in England next week.
Leanne Wood, from near York, and her two children arrived home in the early hours of Sunday morning because of the queues at Calais.
She said: “We arrived early and the queues started forming but it was taking too long because there was no space for the cars.
“The reason for the delay seemed to be British passport control – they seemed to be on a ‘go slow’.
“They knew there would be British families coming back but it was as though they wanted to create misery – to make a point.”
‘The port can’t cope’
Earlier on Saturday afternoon, DFDS warned on social media the queues could potentially last for six hours for people traveling from Calais.
P&O added extra vessels were used for passengers who had missed their booked sailings, to “help with the passengers that have been stuck at border control”, as queues continued into the evening.
It earlier said traffic at the ports in Dunkirk, in France, and Dover, in the UK, was “free-flowing through check-in and border controls” throughout the day.
P&O Ferries tweeted that queues were at about an hour.
Passenger Craig Price, from Essex, told the BBC he spent five hours at Calais Saturday afternoon after driving through Italy and France.
“We arrived at 3 pm and got through at 8 pm,” he said.
“The design of the port does not seem able to cope with the need for French and UK border control,” he said, adding that two-thirds of UK border control booths were manned.
The BBC has approached the Home Office and Border Force for comment.
There were similar wait times in Calais just days earlier on 24 August due to extra traffic arriving from the Eurotunnel.
Eurotunnel Le Shuttle passengers had to leave their vehicles and walk through an emergency service tunnel when the train’s alarms went off.