The Royal London Hospital, Whitechapel, is in "disaster medicine mode" and "no longer providing high standard critical care", according to a memo between clinicians.

It has more than 90 patients in adult critical care units and the "number of people with Covid continues to rise rapidly", according to the message.

An email sent to staff at the hospital reportedly on Thursday, December 31 reads: "We would like to take this opportunity to reiterate the fact we are now in disaster medicine mode.

"We are no longer providing high standard critical care, because we cannot.

"While this is far from ideal, it's the way things are, and the way they have to be for now."

The email was first reported by Dr Julia Patterson, chief executive of campaigning organisation Every Doctor.

The message adds: "Every hospital in north-east London is struggling, some with insufficient oxygen supplies, all with insufficient nursing numbers.

"Believe it or not, Royal London critical care is coping well relative to some sites."

Professor Alistair Chesser, group chief medical officer of Barts Health NHS Trust, said the "rapid expansion of intensive care beds" in the trust's hospitals had led to "changes in the clinical staffing model, in line with national guidance".

He added: "Despite this, our dedicated staff are providing high quality care for all who need it thanks to their dedication and skill."

A source said the phrase "disaster medicine" would be well understood between doctors, and patients should not be discouraged from seeking treatment at the hospital, where staffing levels were within guidelines.

The email said "many nursing staff from a variety of areas have been redeployed to help" and a "further tier of senior trainees" was being added.

Earlier this week, one senior doctor said trusts in London and the South East are considering the option of setting up tents outside hospitals - something normally reserved for sudden events such as terror attacks or industrial disasters - to triage patients.

The NHS in London has been asked to make sure the Nightingale Hospital at the ExCeL, Custom House, is "reactivated and ready to admit patients" as hospitals in the capital struggle.