A furious row has broken out between British Airways and the British Home Office over "dreadful" immigration queues at airports.
The airline launched a scathing attack on the border control operation, complaining that some passengers are being forced to wait in lines for more than an hour upon arrival at Heathrow, the UK's busiest airport.
There are "routinely" just a third of the 29 automatic eGates open at Terminal 5 and they shut "prematurely" at 11pm while customers are still making their way off flights, the carrier claimed.
It added that this is causing "massive queues and frustrating delays".
But the Home Office issued a fierce rebuttal, claiming BA's statement "significantly misrepresents" the experience of the vast majority of passengers arriving at the west London hub.
The British Government department insisted that Border Force officers have kept eGates open beyond 11pm "often to accommodate passengers arriving on delayed British Airways flights".
When the latest eGates were installed in October 2015, the Home Office claimed they would reduce queues and free up Border Force officers to focus on priority work such as cracking down on smugglers or identifying victims of trafficking.
Adult passengers from the UK or European Economic Area with a chipped passport can pass through the facial recognition terminals when they are in use rather than wait for manual checks.
BA's director of Heathrow Raghbir S Pattar called on UK Border Force to operate in the "most efficient and flexible way" to ensure passengers' needs are prioritised.
He said: "It is a constant frustration to us and to our customers that after a long flight they have to stand in queues, sometimes for over an hour, just to get back into the country.
"And it is a dreadful welcome for visitors to the UK to be faced with a packed immigration hall and the prospect of a frustrating delay to the start of their holiday or business trip.
"It adds insult to injury when you're stuck in a queue but can see numerous gates which just aren't being used."
The Home Office said more than 99% of British and European passengers arriving at Heathrow are dealt with within 25 minutes, and there has never been a queue of more than an hour measured for European Union arrivals at Terminal 5.
Some 87% of passengers from outside the European Economic Area are processed within 45 minutes.
A Home Office spokesman said: "The security of our border is paramount, which is why 100% of scheduled passengers are checked when arriving in the UK.
"While every effort is made to keep delays for passengers to a minimum, we make no apology for carrying out this important work."
UK holidaymakers have faced lengthy queues at airports elsewhere in Europe because of tightened border rules.
Britain's aviation minister Lord Callanan said he would urge his counterparts in Portugal, Spain and Italy to "do all they can to reduce queues" after lobby group Airlines For Europe reported that passengers are being forced to stand in immigration lines for "up to four hours".
New European Union rules mean countries must carry out more stringent checks on arriving and departing travellers.
But when Ryanair chief executive Michael O'Leary was asked about the situation earlier this month, he replied that it is "absolutely a replication of what goes on at border control here in the UK".
He said: "Governments are great at passing these regulations and then not putting in place the staffing at airports to actually manage the implementation of those regulations, both here in the UK and in Europe."