The chief executive of NHS Blood and Transplant, Dr Jo Farrar, said the service had an “incredible response” from donors after an earlier appeal last month.

“However, seven weeks on, the need for O negative blood in particular remains critical,” she said.

The latest data shows, external that national stocks of O negative blood are currently running at only 1.6 days in England, well below the six-day target.

The shortage is blamed in part on a ransomware attack on the pathology firm Synnovis last month.

Before a patient can be given a blood transfusion, hospitals routinely check their blood type to make sure the donated blood is compatible.

Since the cyber-attack in June, a number of major London hospitals that contracted with Synnovis, including King’s and Guy’s and St Thomas’, have not been able to run those checks as quickly as normal.

Instead doctors have been forced to use universal O-type blood, which is draining stock levels across the whole system in England.