The opening of a new children's hospital in Edinburgh has been cancelled just hours before patients were set to move in.

Problems with the ventilation system in the new Royal Hospital for Sick Children and Young People were reportedly conveyed to staff in a last-minute meeting today.

Patients, including young children, were set to begin moving from their current building on Friday, and the hospital was due to open fully on Tuesday.

It is replacing the historic sick kids' hospital on the city’s Sciennes Road, which has been treating children since 1895.

READ MORE: Sneak peek inside new state of the art children's hospital in Edinburgh

The ventilation issue was uncovered following final safety checks in the critical care unit, and bosses have decided the hospital requires 'further work to meet national standards'.

The health board has been told to act 'as quickly as practicable' to remedy the issue.

Health Secretary Jeane Freeman said: “There is no greater responsibility of the NHS than to ensure the clinical safety of their patients, not least when those patients are children. In order to be absolutely sure that patient safety is delivered, I have no choice but to postpone NHS Lothian’s planned move to the Royal Hospital for Children and Young People.

“It is vital that patient safety remains paramount, which is why I have asked the health board to stop all moves until assurances have been given that the new site is entirely compliant with the relevant health technical standards.   

“While this issue has been caught by the final safety checks, I am disappointed and deeply concerned that this was not identified earlier. 

"I have asked that Health Facilities Scotland undertake an investigation to determine how the hospital got to this advanced stage before it was discovered that the ventilation system fell below the standards expected. This work will cover both technical and governance aspects of the project.

“We will continue to be in close contact with the health board throughout this period to ensure the health and safety of patients remains the key focus.”

READ MORE: Staff gather for farewell to Edinburgh Sick Kids Hospital as it prepares to close

NHS Lothian chief executive, Tim Davison said: “Patient safety is paramount, and following the handover of the new hospital NHS Lothian has continued to monitor facilities at the new site to ensure all systems are operating to national standards.

“Following advice from an independent advisor, I fully accept the Health Secretary’s decision to reschedule the move to the Royal Hospital for Children and Young People. The air environment is extremely important and can help prevent the occurrence and spread of infection in patients who are already vulnerable.  

“We are extremely disappointed that we cannot move as planned and I am very sorry for the disappointment this will cause to patients, their families and staff affected by this delay. However, patient safety must always come first.”