The extent to which the Border Force failed to meet some immigration-queue targets at Heathrow last month were revealed today.
Figures show that on April 30 there were passport-check queues of up to three hours at Heathrow's Terminal 4.
This was around twice as long as the figure under-fire Immigration Minister Damian Green has suggested in the House of Commons.
The statistics, released by airport operator BAA, showed that, on average, the Border Force failed to meet its target for getting non-EU passport holders through immigration at all Heathrow terminals last month,.
The non-EU target at Terminal 5 (T5) was missed on 23 out of 30 days in April.
The non-EU target was missed on 21 days at Terminal 3 and at Terminal 4, and missed on 12 days at Terminal 1.
There were hour-long queues at T5 on April 10, while there were queues of two hours 35 minutes for non-EU passport holders at T5 on April 17.
But despite these long queues on some days, the targets in April were, on average, met for EU passport holders.
The Border Force admitted that "at times" queues had been too long, while Labour said Mr Green's "complacency in Parliament on Monday has now been shown to be completely misplaced".
Under its targets, the Border Force must get non-EU passport holders through immigration at Heathrow in less than 45 minutes for 95% of the time.
Its target for EU passport holders at Heathrow is less than 25 minutes for 95% of the time.
Border Force monitoring of its targets involves hourly checks, but BAA's monitoring of the April 2012 Border Force performance involved 15-minute checks.
Of particular concern is the fact that at Terminal 5 only 75.7% of non-EU passport holders were through in less than 45 minutes.
This is where British Airways planes take off and land and it is by far the busiest Heathrow terminal in terms of passengers and flights.
Willie Walsh, chief executive of BA's parent company, IAG, has been particularly strong in his condemnation of the long queues at Heathrow, saying the situation is damaging for Britain, particularly in the run-up to the London Olympics.
Next Thursday immigration staff will stage a one-day strike in a bitter dispute over public pensions, threatening huge disruption at airports, including Heathrow.
A Border Force spokesman said: "Border Force and BAA data shows that queuing time targets for UK and EEA citizens were not breached during April. But we know at times queues have been too long.
"That is why we have announced an extra 80 staff for peak times at Heathrow. And it's why we've also engaged an extra 480 people to cover the Olympic period.
"In the longer term, our management and rostering changes will address the issue of queues."
Shadow immigration minister Chris Bryant said: "Damian Green's complacency in Parliament on Monday has now shown to be completely misplaced.
"People are right to feel angry that thanks to the Government's ineptitude and cuts of nearly 900 members of staff, queues at Heathrow have been far too long.
"We need more than just words from the Prime Minister. The Government must get a grip or they will undermine our border security, our business reputation and the British tourism industry."
Public and Commercial Services union general secretary Mark Serwotka said: "The issues of the last few days bring to the public's attention what we have said for a long time - that you can't cut staff and expect to run the same service.
"Clearly, the cuts already made in UK Border Agency have had a major impact and further cuts planned every year until 2015 will make the situation even worse.
"Ministers must now accept what the rest of us can plainly see - that austerity isn't working, and that what we need is investment to improve our public services and get our economy moving again."
The British Air Transport Association (Bata), the trade body representing UK airlines, met Home Secretary Theresa May today.
Afterwards, Bata said the delays were "unacceptable" and that the Border Force should be properly resourced. Bata said the extra money needed should come from the Air Passenger Duty airport departure tax.
* According to the BAA figures, these were the terminal-by-terminal figures for Heathrow in April 2012:
NON-EU PASSPORT HOLDERS
TARGET FIGURE ACHIEVED
Terminal 1 95% 94.5%
Terminal 3 95% 87.0%
Terminal 4 95% 84.4%
Terminal 5 95% 75.7%
EU PASSPORT HOLDERS
TARGET FIGURE ACHIEVED
Terminal 1 95% 99.5%
Terminal 3 95% 99.5%
Terminal 4 95% 99.0%
Terminal 5 95% 98.0%