Passport security checks could lead to longer queues after Brexit unless the Border Staff employs more staff, airports have warned.
The Airport Operators Association (AOA) said tougher security measures for EU nationals could affect everybody flying back into the UK.
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Its comments emerged in a House of Lords inquiry into the movement of people between the EU and UK.
The BBC reports that the the AOA says growth in air traffic has not been matched by an increase in Border Force resources.
However, the Home Office says Border Force can maintain security.
A whistleblower last year told the BBC that staff were struggling to cope with queues to check passports at Heathrow.
The AOA is now concerned that any changes, possibly more stringent, to passport checks will make waiting times longer.
Currently, EU nationals can use ePassport gates when entering the UK, which can be quicker than systems used for passengers outside Europe.
The AOA says that if all overseas passengers have to show their passports manually to Border staff after Brexit, it could lead to an increase in queues at security.
According to the Metro, a Home Office spokesman said: "We are about to begin negotiations with the EU and it would be wrong to set out further positions in advance, but we are clear that Border Force has the capacity to meet passenger demand and maintain security."