Crowds at Heathrow Airport have sparked "super spreader" concerns after pictures emerged of a packed Terminal 2 with limited social distancing.
Pictures and videos of huge queues for passport control have appeared on social media in recent days, despite international travel being largely banned from the UK.
Former British ambassador Peter Westmacott posted a photo of Terminal 2 yesterday captioned: "T2 Heathrow Friday afternoon. No ventilation. Long delays. Super spreading."
While the photo appears to show people arriving into the UK, a number of airlines operate flights to Ireland from the same terminal.
Four flights departed Terminal 2 yesterday bound for the island of Ireland.
Two flights travelled to Dublin airport, one to Cork, and one to Belfast.
As of last Saturday, all passengers arriving into Ireland must have a negative COVID-19 PCR test, taken within 72 hours prior to arrival.
People coming from Britain and South Africa must isolate for 14 days after arrival, even if they take a second coronavirus test five days after arrival.
It comes as British Prime Minister Boris Johnson warned yesterday that the UK coronavirus variant may be more deadly than the original.
I had to fly to Washington via Heathrow as there are no direct flights from Dublin atm. I was travelling from T2 to T5 and there were queues just like that for domestic and flights to Ireland. I literally ran past as fast as I could. It is simply unfathomable that this is allowed
— Vicky Phelan (@PhelanVicky) January 23, 2021
There have been increased calls in recent days for the introduction of a mandatory quarantine period of at least five days for people arriving in Ireland from abroad.
As for UK Government guidelines, Britons are only allowed to go abroad for a small number of "legally permitted reasons" during lockdown.
The scenes at Heathrow Airport yesterday were described as "incredibly worrying" by Labour's shadow home secretary Nick Thomas-Symonds.
A UK Government spokesperson said it is "ultimately up to individual airports to ensure social distancing on site".
However, Heathrow has claimed it is in fact Border Force who are responsible for enforcing the rules.
Additional reporting by IRN