Boris Johnson, London's mayor, has expressed his "serious concern" about long queues for passport control at Heathrow airport.
In a letter to Theresa May, the home secretary, Mr. Johnson said he was looking forward to hearing how the Home Office and the U.K. Border Force planned to save passengers from long waits at immigration before the London Olympics.
He said Heathrow, the country's largest airport, gave "a terrible impression of the U.K." London's reputation as a welcoming place to do business and travel was at stake.
"It is extremely unfortunate that, in a time of economic difficulties, when I as mayor and the government are working so hard to attract inward investment to London and the U.K., that our main port of entry is gaining such a poor reputation," he said.
The long queues are caused by a combination of tougher passport checks, after last autumn's row about the Border Force relaxing procedures too far, and staff cuts at the agency. The Home Office is reducing the force's manpower by about 18 per cent from 2010 to 2015.
Damian Green, the Home Office minister, told MPs on Monday that it was important to maintain a balance between security and putting on a good first impression for visitors arriving at Heathrow.
He said in the Commons that his officials' study of the position last week showed that claims of border desk queues were exaggerated and the longest queue was at Terminal 5 at Heathrow last Friday, where non-EU passengers were forced to wait for 90 minutes. The queues were "significantly less" for EU and U.K. arrivals, he added.
However, Keith Vaz, the chairman of the Commons home affairs select committee who had called for the urgent appearance of the minister, said he had been assured queues had exceeded two hours.
Mr. Green said next week would see the introduction of new measures, including a central control room and rapid reaction teams at Heathrow, as well as new shift patterns, to address the problems.
Waiting times in queues at Heathrow in April have led to many complaints – with no big sports event taking place nearby and no surge in passenger numbers. The worst queues recorded last week were at Terminal 5 on Wednesday afternoon, when some passengers from outside the EU waited about two-and-a-half hours to clear passport control.
London's mayor said that with 80 per cent of visitors to the Olympic Games expected to arrive through Heathrow, the number of passengers at the airport could rise by 45 per cent in the summer.
News of Mr. Johnson's letter came after the Border Force demanded that BAA, Heathrow's operator, stop distributing a leaflet to passengers that blamed the Home Office for the long immigration queues.
BAA prepared a leaflet for distribution at the weekend that said the Home Office had strict security measures in place that could result in very long delays at immigration.
In an e-mail to BAA, Marc Owen, a senior Border Force official at Heathrow, objected to the leaflet, describing it as inflammatory, and saying it could increase tensions inside immigration halls.
BAA has agreed not to hand out the leaflet, but the episode has highlighted significant tensions between it and officials.
BAA declined to comment on its relationship with the Border Force, but said: "Immigration waiting times during peak periods at Heathrow recently have been unacceptable and we have called on the Home Office to address the problem as a matter of urgency."
Heathrow's operator has grown increasingly concerned at immigration queues at three of the airport's terminals this year.
Downing Street said last week's problems there had been caused by flight disruptions and bad weather.
It added: "Clearly we want to do everything we can to keep disruption to a minimum. But we have to make sure we don't do anything to compromise border security."
The Border Force said: "We are flexibly deploying staff in the right numbers at the right times, meaning that the vast majority of passengers pass through immigration controls quickly."
Additional reporting by George Parker