The new EU system for registering travellers from third countries is due to come into force in October.
Britons heading to Europe could face waits of 14 hours or more at border controls under a new scheme, MPs have been told.
The Port of Dover and the surrounding area could be hit by major disruption when the EU Entry-Exit System launches unless measures are introduced to prevent delays, Parliament’s European Scrutiny Committee heard.
Ashford Borough Council told the cross-party group that 14-hour queues are a “reasonable worst-case” scenario if the scheme is implemented as planned in October.
Chairman of the European Scrutiny Committee, Sir Bill Cash, said: “Queues of more than 14 hours, vehicles backed up along major roads, businesses starved of footfall: this evidence paints an alarming picture of the possible risks surrounding the Entry-Exit System’s implementation.
“Clearly, this policy could have a very serious impact, not only for tourists and travel operators but also for local businesses.
“I implore decision-makers on both sides of the Channel to take note of this evidence.
“The scheme is due to be implemented in October this year; the clock is ticking, and these issues must be urgently addressed.”
Under the much-delayed scheme, people from non-EU countries will be registered each time they cross a border in or out of the EU.
The Port of Dover and surrounding roads have seen multiple episodes of gridlocked traffic over the past few years, with post-Brexit checks adding to waiting times.
Tourist organisation Visit Kent voiced concerns that delays caused by the new system could have a knock-on effect on local businesses.
Ashford Council warned that 14-hour delays at the port will likely see queues along the A20 and M20, which could block access to staff and tourist traffic at Eurotunnel in Folkestone.
Eurostar said that without upgrades, terminals could see queues of more than an hour at peak times.
High Speed 1, which runs UK high-speed rail services, said that the decision not to enable online pre-registration would “put enormous pressure on infrastructure at St Pancras International”.
Downing Street downplayed the likelihood of such lengthy delays.
“I’m not aware of that being something that will happen,” the Prime Minister’s official spokesman said.