Transport secretary Chris Grayling has said trucks coming into Dover will be checked after the UK leaves the European Union.
Grayling told BBC Question Time it would be "unrealistic" to impose checks on lorries coming into the port, which, according to an Imperial College London study, could introduce traffic queues of up to 29 miles based on two-minute checks.
He said the UK would avoid such time-consuming checks through maintaining a "seamless" electronic border.
Ministers have previously stated that a hard border in Ireland would similarly be avoided through the use of technology at the border between Northern Ireland and the Republic of Ireland, which will stay in the Single Market and customs union after Brexit.
Imperial College London report said just two extra minutes on each vehicle check could more than triple existing queues (Source: Getty)
"We will maintain a free flowing border at Dover – we will not impose checks in the port," Grayling said. "We don't check lorries now – we're not going to be checking lorries in Dover in the future.
"The only reason we would have queues at the border is if we put in place restrictions that created those queues – we are not going to do that."
Imports from, and exports to, countries from outside the European Union are currently subject to customs controls, but goods from the EU are free to be moved on with no extra checks.
Andy McDonald, Labour's shadow transport secretary, said Grayling's comments showed "how unprepared" the government was in leaving the EU.
Chris Grayling let the cat out of the bag by exposing how unprepared the government are for leaving the European Union. The government said leaving the EU is about regaining control of our borders but the transport secretary’s plan would achieve the exact opposite.
The only serious and workable proposal to avoid a gridlock at our ports and to ensure the flow of goods in and out of the country post-Brexit is Labour’s plan for a new comprehensive UK-EU customs union with our European neighbours.
Best for Britain spokesperson Paul Butters said Grayling's stance was "pie in the sky thinking".
It's fitting that Chris Grayling took the opportunity on national Pi day to spell out this Government's pie in the sky thinking. The government plans to take back control of Britain's border by not having any.
To be clear: you cannot have a clean break from the EU and expect no border checks – that's simply the nature of having tariffs.