Dover could face gridlock on a daily basis and become a "magnet" for illegal immigration if Britain's departure from the EU is not handled smoothly, local officials have warned.
The Port of Dover's chief executive, Tim Waggott, fears the UK will suffer if there are customs issues post Brexit - jeopardising trade and endangering jobs nationwide.
He told Sky News Presenter Sophy Ridge: "Certainly prices could rise on supermarket shelves. Prices of foreign manufacturers could rise, the UK could become less competitive, lots of production lines in the Midlands and the North could close if we don't get this right."
Every year, £119bn of trade flows through the Port of Dover, as well as millions of freight vehicles.
Mr Waggott claims that even small delays in processing these huge volumes of freight could cause major problems - as the port currently handles about 99 miles (160km) worth of traffic on busy days.
"We overflow our available space two or three times a week, at peak times. That will be a daily occurrence," he said.
However, not everyone fears the worst.
Robert Hardy, operations director at the Motis freight service in Dover, said he saw Brexit as an opportunity rather than a threat - and said concerns about traffic flowing through the port efficiently have been raised long before the UK's vote to leave.
He explained: "It was 25 years ago there were only a million trucks a year. There are four million trucks a year now. Technology has come on leaps and bounds and I think that technology can help smooth the path.
"If we're saying that everything requires customs clearance again post Brexit, 98% of that will be processed concurrently in five-minute chunks. I don't see it as such a large issue."
As well as Dover's important role in trade between the UK and the rest of the continent, 13 million passengers also rely on the port each year.
But Brexit could also have huge consequences for immigration, as it may result in the border being moved from Calais to the UK.
Lucy Moreton, general secretary of the ISU union for borders, immigration and customs, says losing the Border Force's presence in France means there would be no way to stop asylum seekers from boarding lorries bound for the UK.
She described a "doomsday scenario" where tens of thousands of people attempt to arrive on UK soil.
"Once an individual has got inside a container, got on board a ferry, they are, to all intents and purposes, here," Ms Moreton told Sky News.
"We're going to have to hear that asylum claim, we're going to have to support them during that claim. At the moment, that can take 18 to 24 months, if not longer.
"It risks making the UK even more of a magnet for asylum seekers and migration than it already is."
At the moment, the entry of individuals holding EU passports is not controlled by UK border officials - but Ms Moreton expressed concern that changes to the immigration system after Brexit could leave the agency massively understaffed.
"If we can no longer do that… we could need at least as many staff again as we have now. We have about 8,000 border officers right now. We could easily need to double that," she said.
The next two years of Brexit negotiations could prove decisive for Dover, where 62% of voters backed Brexit in last June's referendum.
:: Watch the full interview on Sophy Ridge on Sunday at 10am on Sky News