More than 800 patients suspected of having cancer could have had their diagnosis delayed because of an administrative error, a hospital trust has admitted.

West Hertfordshire Hospitals Trust said at least one person may have died as a result of the mistakes and 121 patients are still yet to have their case reviewed.

Between January 2010 and November 2013 patients who failed to turn up for their first appointment after being urgently referred for cancer tests were not always offered a second appointment and in some cases were discharged by the trust - in contravention of NHS guidelines.

In total, 810 patients have been contacted by the trust to have their cases reviewed and of these 686 have been told there were no clinical concerns over their care.

But the trust admitted that the delay in seeing one patient may have contributed to their death, while the death of another patient whose diagnosis was delayed is not thought to have been preventable. The trust has apologised to the families of both patients.

The trust, which is made up of Hemel Hempstead Hospital, Watford General Hospital and St Albans City Hospital, discovered the error following the launch of its new management team in November.

Samantha Jones, chief executive of the trust, said: “It is absolutely clear that the trust was not always following the correct administrative processes for these patients and we let them down.

“These concerns date back a number of years and were identified as part of the new management team’s commitment to improve the way we administer and manage patient care.

“I would like to apologise to each and every patient who has been affected and particularly to the relatives of those who have since died.

“We have of course made significant changes to help prevent this ever happening again and will share the outcome of our investigations with those affected and with the wider public.”

The trust said it has since implemented a new IT system, retrained staff and holds daily reviews of all patients who miss cancer appointments.

Hemel Hempstead Conservative MP Mike Penning said: “I am shocked to learn that Hemel Hempstead cancer patients have been allowed to slip through the net due to the incorrect use of procedures. They have been badly let down and it is very upsetting.

“A national review is needed to make sure that the problem is not being repeated elsewhere and that no more patients are let down in this way.

“I commend current chief executive Samantha Jones and her team for discovering the problem and facing it head on to ensure that no more patients suffer the same break-down in their care.”

The trust said it was “confident” it has contacted everyone affected by the errors but anyone concerned should contact their GP or call the trust’s information line on 01923 217 100.