Large queues have formed for ferries and trains forcing holidaymakers to wait for hours.
Cars faced 90-minute waits at the Port of Dover on Good Friday, and were seen snaking all the way to the nearby town, with lorries thought to be stretching back further.
Meanwhile, images of thousands of rail passengers queueing at stations in London have been shared on social media, as travellers described being delayed for hours as a result of service disruption.
Euston Station is closed from April 7 to 10 for track improvements while planned works are also affecting the Elizabeth line and some National Rail services.
Ruaridh Pritchard, a writer from the capital, was delayed for three hours as a result of crowds and service reductions on his way to Stockport, Greater Manchester, for an Easter weekend with friends.
“St Pancras was mayhem – limited crowd control,” the 33-year-old told the PA news agency.
“Staff are doing the best they could under the circumstances. Lots of people arguing and pushing – it was like the last train out of Saigon.
“(It has) kind of put a dampener on the weekend, I’ve lost half a day of Easter.”
Sophie Earish, a student from Wembley Park, said her normal 20-minute Tube journey to St Pancras took an hour due to closures on the Metropolitan and Jubilee lines.
“I didn’t realise Euston was closed this weekend causing this mess,” she told PA.
“The queues to get to trains on the platforms were chaotic… why do they think it’s acceptable to do engineering works over the Easter weekend? It’s ridiculous, it seems to be the same every year.”
It came after P&O Ferries and operator DFDS were reporting delays of between 60 and 90 minutes to the port’s entrance while Irish Ferries advised people to allow up to three hours before their travel time.
P&O Ferries said in the afternoon: “There are currently large queues at the entrance to the Port of Dover of at least 60-90 minutes.
“Please allow additional time on your journey if possible and rest assured should you miss your crossing you will be on the next available.”
Doug Bannister, chief executive of the Port of Dover, told BBC Radio 4’s Today programme: “First of all, the weather’s clear, the ferries are sailing well, and all that sort of stuff, this weekend was always scheduled to be about 30% lighter than last weekend, today being the busier day.
“What we did is we worked with our ferry operators to try and spread the demand across the three days rather than all on this day.
“I know that that’s challenging for the coach industry because they have itineraries that they want to maintain, but they’ve worked with the ferry operators to be able to do that, and that’s been successful.
“We’ve also installed a new facility to expand our processing at the borders for coaches, that’s operational, I just saw one goes through in just shy of 10 minutes.
“It’s going to be a busy day, we’re running probably about an hour to an hour and a half to get through border controls at the moment, and we will peak through probably early afternoon, and then it will start to slow down after that.”
He said holidaymakers should bring drinks, food and entertainment for children if they are arriving at the port.
Nichola Mallon, of Logistics UK, talking about lorry drivers using the port, told Sky News: “If they’re waiting considerable periods of time, that becomes a driver welfare issue and so that’s why we’re working very closely with the Kent resilience forum, and to make sure that we can minimise delays.
“In fact, I have a number of meetings today as we closely monitor the situation and make sure that contingency plans are in place if needed, and people are working very hard on that.
“Our message to our members would be to check with your ferry operator to make sure that you’re aware of the latest guidance, make sure that you’ve completed all your paperwork before you head there and have supplies there, just in case, and make sure that you leave enough time to accommodate any delays.”
At one point on Thursday, there were queues of “approximately 90 minutes” for passport checks by French officials at the port as the Easter rush kicked off amid “high volumes of traffic”, DFDS said.
Delays at Dover have been blamed on French border officials carrying out extra checks and stamping UK passports following Brexit.
Port officials said they held an “urgent review” with ferry operators and the French authorities in an attempt to avoid a repeat of last weekend’s delays.
A general strike in France in a row over pension reforms is also causing disruption.
About 400,000 people joined a protest against President Emmanuel Macron’s pension reforms in Paris on Thursday, the French CGT union reportedly said.