London's mayor warned Monday that long delays for passengers arriving at the city's largest airport risk damaging Britain's reputation in the run-up to this summer's Olympic Games.
Boris Johnson wrote to Home Secretary Theresa May amid increasing concerns over lengthy lines at border control desks for those arriving at Heathrow Airport.
Passengers have complained of frustrating delays, on some occasions of more than an hour, because of lengthy passport and visa checks and an apparent lack of border staff.
Johnson said the delays were giving "a terrible impression of the U.K." and demanded action ahead of a busy summer during which Britain will mark Queen Elizabeth II's 60th anniversary as monarch in June, and hold the Olympics.
"This summer, with the Queen's Diamond Jubilee and the London Games, gives us a once in generation's opportunity to promote what is very best about London and the U.K.," Johnson wrote.
"It is critical for the success of these events that visitors from across the globe have a great experience from beginning to the end of their stay," he told May, who is responsible for Britain's borders.
Heathrow typically handles an average of 190,000 arriving and departing passengers each day, but is braced for a major influx during the July 27-August 12 Olympics.
Johnson said that about 80 percent of visitors and participants arriving for the Olympics will use Heathrow, which would "place short term additional pressures on the system."
Prime Minister David Cameron's spokesman Steve Field said recent disruption had been partly caused by heavy wind and rain, meaning some planes arrived into Heathrow later than planned.
"The problem is, we have seen some particular circumstances — for example, the severe weather conditions over the last few days — which have meant flights have landed later than expected," he said.
However, he insisted that authorities were well placed to cope with the influx of visitors during the Olympics.
A contingency force of retired border staff and workers at other government departments who have been specially trained will be able step in to help ease queues, he said.
"Our objective is to keep disruption to a minimum while at the same time making sure border security is not jeopardized in any way," he said.
Lawmakers and Heathrow's operator BAA Ltd. have called for additional border staff, mindful of the disruption experienced last summer, when Britain's then border chief relaxed some passport checks during the busy tourist season simply to handle the demand.
Field said that May will meet with the British Air Transport Association, the airline industry group, to discuss problems over recent days.
Parliament's Home Affairs Select Committee plans to question Britain's Immigration Minister Damian Green on the issue next month.