Barts and the London NHS Trust has apologised to 442 patients who were not seen within maximum government waiting limits because of inadequate management systems.

The patients waited an average of six weeks longer than the 13-week waiting time national standard for an outpatient appointment.

The trust said the delays were caused by inadequate management systems within the Outpatient Appointment Office.

The trust has launched a "serious untoward incident" investigation to identify the root cause of the issue and why management systems did not alert the organisation to delays sooner.

In a statement the trust said that no patient had come to "direct" clinical harm as a result of the delays.

Last April Barts and The London NHS Trust installed the Cerner Millennium Care Records Service as part of the NHS's £12.7bn National Programme for IT. After the go-live last year it had difficulty gaining an overview of which patients had been treated for what. Some patients with suspected cancer had their appointments delayed.

Of the latest incident to come to light of delays in the appointments for 442 patients, the trust said matters appear to have been "compounded by the inflexibility of the Care Record Service computer system".