Coach operators have claimed their vehicles were “treated unfairly” after thousands of passengers were stranded at the Port of Dover for up to 24 hours over the weekend.

Trade association the Confederation of Passenger Transport (CPT) called for “crisis talks” with the Government, the Kent port and ferry companies to “resolve this mess once and for all”.

Many holidaymakers travelling by coach during the weekend – the start of the Easter holiday period for many schools – were delayed entering the port and being processed.

The queues had cleared by Monday morning but there are fears the congestion could return during other peak periods due to French border officials carrying out extra checks and stamping UK passports following Brexit.

Downing Street acknowledged that “new processes” introduced following the UK’s withdrawal from the European Union contributed to the disruption, while Labour leader Sir Keir Starmer said “of course Brexit has had an impact”.

The CPT claimed coaches were “held back behind cars and HGVs”, meaning their passengers were “delayed between eight and 24 hours”.

It fears the situation “will only get worse” when the start of the summer holiday period arrives.

Something’s clearly wrong when a coach - the most efficient way to transport large numbers of people across the Channel - is treated unfairly compared to other vehicles

Chief executive Graham Vidler said: “Something’s clearly wrong when a coach – the most efficient way to transport large numbers of people across the Channel – is treated unfairly compared to other vehicles.

“Coaches provide the answer to the environmental and congestion issues we’re trying to address, yet some of our spacious vehicles full of students and holidaymakers were left stranded.

“The procedures to enter the EU should not have a negative impact on people who don’t want to fly or drive by car to continental Europe.

“We’re calling on the Government, the Port of Dover and ferry companies to get round the table with the coach sector to resolve this mess once and for all.”

Disruption was first reported on Friday when the port declared a critical incident and said the delays were “due to lengthy French border processes and sheer volume”.

Home Secretary Suella Braverman told the Sophy Ridge On Sunday programme on Sky News it would not be fair to view the delays as “an adverse effect of Brexit”.

On Monday, Prime Minister Rishi Sunak’s official spokesman told reporters: “I think there were a combination of factors that took place over the weekend.”

Asked whether Brexit was one of the factors, the spokesman said the French were “inspecting and stamping every single passport”.

The spokesman said: “We recognise there are new processes in place – that’s why authorities were given a long time to prepare for the new checks, including during the transition period, of course.

“And we are in discussion with our French counterparts about how we can further improve the flow of traffic.”

Sir Keir told LBC: “Of course Brexit has had an impact – there are more checks to be done.

“That doesn’t mean that I am advocating a reversal of Brexit, I am not. I have always said there is no case now for going back in.”

He added: “Once we left, it was obvious that what had to happen at the border would change.

“Whichever way you voted, that was obvious. Whichever way you voted, you are entitled to have a Government that recognises that and plans ahead.

“Yet again we have got to the first big holiday of the year and we have got queues, to the great frustration of many families trying to get out to have a well-earned holiday, and I think my message to the Government, their message, would be ‘Get a grip’.”

It is clear that the Brexit impact has not been adequately planned for

Eurostar revealed earlier this year that it is forced to leave hundreds of seats empty on trains to and from London St Pancras to avoid long queues at stations.

The cross-Channel train operator said this is largely due to a reduction in the number of border officials, but also blamed the stamping of UK passports post-Brexit.

Julia Lo Bue-Said, chief executive of Advantage Travel Partnership, the UK’s largest network of independent travel agents, described the situation at Dover as “distressing”.

She said: “It is clear that the Brexit impact has not been adequately planned for.”

Meanwhile, Downing Street said “discussions” are continuing with Civil Service unions as more than 1,000 members of the Public and Commercial Services union (PCS) at eight Passport Office sites have walked out.

Security guards at Heathrow Airport from the Unite union are also on strike, but there did not appear to be delays in processing departing passengers.