New passport checks have doubled processing times and will cause chaos this summer, a trade union says.
Biometric passports have added security features
Officials are taking up to 10 seconds where before they needed just three or four seconds to check passports, the Immigration Service Union has said.
Laser devices which read biometric passports are among the causes of the extra delays, the union claims.
The government said the checks had to be made but admitted late flight time changes could cause immigration queues.
John Tincey, vice-chairman of the union, said there were bad queues in 2006 and this summer the situation would be worse.
He said at times there was so little room in the arrivals areas that people were forced to wait on aircraft.
Airports used by low-cost airlines, such as Stansted, Gatwick, Luton and Birmingham were usually worst hit.
He said: "Now it is going to take twice as long and this summer is going to be a crisis period. It is going to be much worse than last year."
A spokesman for the government's Border and Immigration Agency said there were times when flight arrival times varied from the schedules which could lead to a "bunching of passengers" at immigration controls.
However he added: "While allowing most passengers into the UK quickly, thorough checks are necessary to identify criminals, prevent illegal immigration and protect the public."
The hi-tech biometric documents have added security features such as a chip holding the carrier's facial details.
New passports also feature pages with intricate designs and new complex watermarks.