Passport control queues at Heathrow Airport reached two and a half hours last month, new figures show.
Data obtained by airline Virgin Atlantic shows that UK Border Force only achieved its target of processing 95% of passengers from outside the European Economic Area (EEA) within 45 minutes on just one day in July.
The longest queues happened on July 6, when non-EEA visitors spent up to two hours and 36 minutes waiting in immigration queues.
The chief executive of Virgin Atlantic called on Border Forces to take action on the "unacceptable queue times".
He added it is important for the Government to give a "great first impression" to visitors at a time when the UK needs to show it is open for business.
Heathrow chief executive John Holland-Kaye has called for the Home Office to allow visitors from “low risk countries such as the US” to use the same electronic gates that European Union citizens can access.
He previously blamed a “lack of staffing” for long queues during an England World Cup game.
The Home Office said the queues were partially caused by a computer failure and a large number of vulnerable adults and children arriving.
British Airways chief executive Alex Cruz warned last week that Heathrow’s queues were “significantly worse” than elsewhere in the continent.
Writing in The Times, Mr Cruz said: “Two-hour queues are fast becoming the norm.”
A Home Office spokesman said: “The vast majority of people who arrive at Heathrow get through the border within our service standards.
“But we understand the frustration for those who have experienced longer waits and remain fully committed to working with our partners to reduce waiting times as far as is possible.
“At the same time, we will not compromise the essential checks we carry out at the border which keep our country safe.