Some hospitals are failing to accurately monitor how long thousands of their patients are waiting for treatment, a report has found.
Research by the National Audit Office (NAO) discovered trusts in England were often "mis-recording" data, with some saying either patients waited less time than they did for treatment, or longer.
NHS targets say 90% of admitted hospital patients should start their treatment within 18 weeks.
Of those patients who do not need admitting to hospital, 95% should be seen within 18 weeks of referral by their GP.
The NAO report reviewed 650 orthopaedic patient waiting times across seven hospital trusts including Northampton General Hospital NHS Trust.
- 94 cases were reviewed at Northampton Hospital
- 53 cases (56%) were all correct
- In 27 cases (29%) the NAO found incomplete records
- There was at least one error found in 14 cases (15%)
The report said mis-recording of data was identified at The North West London, Barnet and Chase Farm and Colchester hospital trusts.
At Colchester Hospital University NHS Foundation Trust, police are already investigating allegations that cancer waiting times were deliberately falsified.
A Care Quality Commission (CQC) report into Colchester found that, in 22 cases, the treatment dates recorded on the system had been changed.
A spokesman for Colchester Hospital University NHS Foundation Trust:
“The Trust has made some serious mistakes in the accuracy of its reporting of cancer waiting times and we are working hard to put things right."