NHS data has shown 35 patients were left waiting more than 12 hours at Edinburgh Royal Infirmary accounting to the worst figures since weekly recording began.
The capital’s A&E department seen the worst waiting times in Scotland, with 79.6 per cent of patients being seen within four hours, compared to the Government target of 95 per cent.
Health bosses have apologised to patients and said the spike was due to an increased number of seriously ill patients who needed urgent treatment.
Lothian Labour MSP Sarah Boyack said the figures were “unacceptable” and questioned whether patients are being forced to visit A&E departments due to lack of NHS facilities in the community.
She said it was particularly worrying that Edinburgh Royal Infirmary has the “worst performance rate in the whole of Scotland”.
Jim Crombie, chief officer of acute services at NHS Lothian, said: “I would like to apologise to anyone who has had a long wait.
“Our teams always aspire to at least achieve and often exceed the nationally agreed four-hour waiting time standard, but this has been a very challenging time.
“Our dedicated teams of staff provided care and treatment to a higher than normal number of patients with serious illnesses and they worked extremely hard to ensure patients were seen as quickly as possible, but we recognise that we fell below our own expectations and we are working hard to improve our performance.”