The problems faced by motorists seeking to leave Dover are not replicated at other Channel ports – where French border formalities take place at the destination, our travel correspondent Simon Calder writes.

Brittany Ferries says it has some availability on services from Portsmouth, Poole and Plymouth this weekend.

Paul Acheson, sales and marketing director for the French ferry firm said: “We feel for all holiday makers struggling with travel through Dover today, as well as our friends and colleagues at ferry companies operating on short-sea routes.

“Our message today is not that we want to profit from misfortune. However, services are running smoothly through our ports and for passengers who are really stuck or if problems persist in Dover this weekend, Brittany Ferries may be in a position to help.”

The foreign secretary has labelled the delays and queues at Dover “unacceptable”, calling it an “entirely avoidable” situation after a “critical incident” was declared by the Port of Dover.

Liz Truss said in a statement: “This awful situation should have been entirely avoidable and is 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. We will be working with the French authorities to find a solution.”

Holidaymakers are being warned that Saturday is expected to be even busier for travelling to Calais via Dover or Folkstone.

It comes after the beginning of the school holidays today saw travellers stuck in queues for up to six hours in Dover.

Jack Cousens, head of roads policy for the AA, said: “As the schools closed their doors fully yesterday, Saturday could prove busier still this weekend.

“Drivers should continue to expect disruption and delays on major holiday routes to the south-west, eastern coast and ports of Dover and Folkestone.

“While many have decided to go at the start of the summer holidays, between now and the beginning of September when schools return, each Friday and Saturday will be busy on our roads.

“This is because these are the main switchover days for holiday lets.”

A statement by the prefect of the Hauts-de-France region – where Calais is situated – states that British media reports that French border police did not provide enough staff “must be corrected”.

The retaliatory statement by the region’s defence and security prefect Georges-Francois Leclerc was tweeted by the French embassy in the UK.

He said that staffing was provided but more than one hour later than originally planned.

It comes as Brits attempting to sail to France are reporting waits of about six hours in Dover at the beginning of the school holidays, for which Dover has blamed French authorities for “woefully inadequate staffing”.

Grant Shapps has said he is “working closely” with his French counterpart after a “critical incident” was declared by the Port of Dover because of six-hour-long queues.

The transport secretary tweeted: “There’s been severe delays today at Dover & so I’m working closely with my opposite number Clement Beaune to address the issues that caused tailbacks.

“I welcome his commitment that both Britain & France will work closely to minimise further disruption so people can get away quickly.”

The chief executive of the Port of Dover has described being “let down” by poor resourcing at the French border as “immensely frustrating”, as travellers faced lengthy queues at the beginning of their summer getaway.

Doug Bannister stopped short of guaranteeing the backlog would clear in the coming days, but pledged that officials are doing all they can to address issues.

Apologising for the situation on Friday - one of the busiest periods for foreign travel from the UK as most schools in England and Wales break up for summer - he said they had been “let down” by French authorities.

He told BBC News: “I am so sorry that the travellers we have going to the port today are being impacted.

“To be let down in the way that we have with inadequate resources and slow processes through the border is just immensely frustrating.

“We’ve shared in granular detail, on an hour-by-hour basis, the amount of traffic we were anticipating, so it was completely known what we needed to have in place at the French border.”

He said Saturday is also likely to be busy, adding it is “just the start of a very busy summer for us”.

Asked whether he can reassure travellers planning a trip over the coming days that the backlog will ease, he said: “I really wish I could - we’re putting all the attention we possibly can do on ensuring there will be enough resources in place to manage this very busy first weekend of the summer.”

Passengers travelling to Dover to catch a ferry to France are still being warned of “long wait times”.

Ferry company DFDS tweeted at 3.30pm: “DOVER-FRANCE IMPORTANT: We are expecting long wait times to complete controls, please take this into consideration when travelling to the port, factoring in sufficient breaks for food and water before arriving.”

The issue is being exacerbated by the continuing closure of the M20 eastbound between J11 and J12 after an earlier collision.

“There are long delays on the approach which is adding to the congestion in the area for the ongoing issues at the Port of Dover,” said National Highways. “Access to Eurotunnel remains open from both the M20 and the A20.”

Pure Brexit took effect at 11pm, British time, on 31 December 2020. So why should the decision to leave the European Union suddenly be afflicting travellers who want to return to the EU, albeit temporarily on holiday?

Because this is the first real peak weekend for cross-Channel travellers from Dover since the Brexit transition phase ended.

Only now are we able to see clearly the results of the choice that we made in the 2016 EU referendum.

As members of the European Union we helped to draw up the rules for “third-country nationals”. In the withdrawal treaty, ministers asked for us to become subject to those rules.

Read The Independent travel correspondent Simon Calder’s full analysis:

There are severe delays on the approach to the Port of Dover due a closure of the M20 eastbound between J11 (Westenhanger/Hythe) and J12, and a closure of the A20 eastbound Roundhill Tunnel.

This is due to a “serious collision” earlier, according to National Highways Southeast.

“The westbound carriageway is now OPEN,” it tweeted.

“However severe delays remain in both directions. Access to Eurotunnel remains open from both the M20 and the A20.”

Queues of four to five hours are still being reported at Dover Port.

Key operator P&O Ferries tweeted: “There are currently queues of up to 4/5 hrs to clear the approach roads and border checks in Dover.

“Check in is free flowing. Our next departures are: 14.00 ETD 14.30 and 16.05 and 17.25.

“Rest assured, if you miss your sailing you will be on the next available one.”