Heathrow passengers faced further delays on Saturday after Terminal 5 was hit by overcrowding.
Holidaymakers were delayed by up to five hours on Friday as they cleared immigration. There were complaints they were not provided with water, ventilation or toilet facilities.
Pregnant women and pensioners were among those forced to queue for long periods of time, while a number of people were said to have fallen ill, with reports of people vomiting, fainting and suffering panic attacks in the cramped conditions.
One eyewitness wrote on Instagram: “Queues snaking up and down corridors in every direction, kids crying, the water clearly dumped in boxes earlier entirely cleared out by 8.30 when I landed and empties strewn everywhere (people desperate enough to be shaking them to try and find an abandoned full one), exhausted mothers breastfeeding in the queue, few staff.”
Airport officials said the “unacceptable” delays were as a result of a lack of Border Force officials on duty at the terminal with arrivals quickly overwhelming immigration staff.
A Heathrow spokesperson said: “We are very sorry that passengers faced unacceptable queueing times in immigration due to too few Border Force officers on duty.
“Border Force were aware of the extra demand from families and we are very disappointed that they did not provide sufficient resource.
“We have additional Heathrow colleagues to support in managing queues and to hand out passenger welfare including water but we need every immigration desk to be staffed at peak times.
“We have escalated this with Border Force and expect them to provide a better service over the remainder of the weekend.”
The Telegraph has contacted Border Force for comment.