One in four of all non-European passengers arriving at Terminal 5 at London's Heathrow airport last month had to wait longer than the target time of 45 minutes to get through immigration, according to UK Border data.
Heathrow owner BAA said on Thursday the Border Force's monthly performance data showed that 24 percent of non-European passengers had to wait longer than 45 minutes at Heathrow's Terminal 5 during April.
It added that the target was missed on 23 out of the 30 days.
The Border Force, run by Britain's Home Office, targets an average 45-minute waiting time for non-European passport holders and an average 25-minute waiting time for European, including UK, passport holders.
Passengers arriving at Heathrow, Europe's busiest airport, have suffered lengthy delays at immigration in the past week.
Passengers have complained of empty border control desks and the failure of iris scanners brought in to speed up the processing of arrivals.
Ferrovial-owned BAA also said 13 percent of non-European passengers at Terminal 3 had to wait longer than 45 minutes, while 15 percent had to wait longer than the target at Terminal 4.
The longest waiting time was at Terminal 4 on April 30, when it took three hours for some passengers to get to the immigration desks.
Airlines using Heathrow airport said on Tuesday they would consider paying higher landing fees to cut delays at the British hub.