Patients, staff and services were due to be transferred from the existing Royal Hospital for Sick Children to the new site at the Royal Infirmary of Edinburgh next week. 

The new building in Little France was due to open on Tuesday and the current hospital in Sciennes was scheduled to close on the same day.

But health secretary Jeane Freeman said she had no option but to delay the opening after it was found that the ventilation system within the critical care department in the new hospital requires further work to meet national standards.

Ms Freeman has directed the health board to act as quickly as practicable to ensure all aspects of the hospital, including the ventilation system, meet the necessary national standards. The board of NHS Lothian has been instructed to set out their plan to phase the move from the old hospital to the new site once it is safe to do so.

This work will be supported by Health Facilities Scotland and Health Protection Scotland and final decisions will be taken by the Scottish Government.

The health secretary 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.   

“Departments within the hospital will move over on a phased basis as soon as it is safe to do so. This work will benefit from external quality assurance from Health Facilities Scotland and Health Protection Scotland and the plan for these moves will be submitted to Scottish Government for approval.

“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.”

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.”

The much-delayed new Royal Hospital for Sick Children in Edinburgh is a £150m project to replace facilities for children at Sciennes near the centre of Edinburgh, and at the Western General Hospital and Royal Edinburgh Hospital, with a purpose-built complex.

The hospital was originally supposed to be open by the winter of 2012, only to be held up by a protracted land swap deal.

Work then began on the project with an initial opening date of autumn 2017. The was put back after Dunne Group and JB Brickwork, two of the companies working on construction of the hospital, entered administration and provisional liquidation respectively resulting in a temporary pause to their work streams.

Further delays were caused by factors including bad weather.