More than 30 A&E patients at Edinburgh Royal Infirmary had to wait up to 17 hours to be seen last week, it has emerged.

Hospital staff were sent an urgent memo after a high number of admissions to the emergency department on Thursday, April 20.

The email was sent to staff after 36 people waited up to 17 hours to get a bed.

It said the situation was "in extremis" and appealed for staff to help find beds for the new admissions.

NHS Lothian said it worked hard with colleagues at other sites to resolve the issue within a few hours.

Some patients were moved to other hospitals to ease pressure at the infirmary.

Scottish Conservative public health spokesman Miles Briggs said: "These A&E waiting times are totally unacceptable and another indication of the massive pressure on NHS services in Lothian which are clearly struggling to cope.

"The SNP government, which is consistently failing to meet its A&E targets, needs to get an urgent grip on this situation and support hard-working NHS staff locally."

According to statistics published on Tuesday, the hospital has managed to handle between 94% and 97% of patients within four hours since the end of January.

Lyn McDonald, site director at the hospital, said: "On Thursday, April 20, the Royal Infirmary of Edinburgh emergency department had an extremely busy day, particularly in the late afternoon and early evening, after a busy Easter weekend.

"The number of attendances at the department were higher than average, which meant that the site admitted an additional 20 patients more than is normally predicted.

"This resulted in a number of patients in the emergency department waiting to be admitted."

She continued: "In response, services across the site were alerted and asked to assist with patient flow.

"Additionally, other sites and across health and social care responded and assisted appropriately. All of these measures allowed the site to return to normal within a few hours."

Health secretary Shona Robison responded to the memo at the Scottish Parliament.

She told MSPs: "Occasionally, particular A&E departments will experience a surge in demand that will happen for a variety of reasons.

"At the RIE, the issue was a post-Easter surge in demand, with high levels of attendances on Thursday, April 20.

"What they then do is what any emergency department will do, they ask for beds to be released as quickly as possible."

She insisted performance at the hospital had "returned to normal within a few hours of that surge."