Police have been asked to investigate a “malicious campaign” against a hospital doctor after letters alleging poor care were sent to three patients and their families.

The letters were sent to patients of Changez Jadun, a brain surgeon at the University Hospital of North Staffordshire Trust.

Dr Jadun has previously been suspended by the trust for 18 months after concerns were raised about his fitness to practise in 2009 and 2011.He was cleared of any wrongdoing following an investigation.

One family received two anonymous letters earlier this year stating their relative “had undergone serious harm as a direct consequence of a brain surgical procedure.”

The letters urged the families to contact the press, the health service ombudsman and their MP.

The trust has said it is possible a fourth family had also received a letter, and it is investigating.After learning of the letters, the trust asked expert radiologist Andrew Molyneux to review the care the patients had received. He found no problems.

In a statement the trust said: “University Hospital of North Staffordshire is now treating this as a malicious campaign against one of its doctors and will be contacting the local police to progress a thorough investigation.”

Medical director Gavin Russell said: “We believe that this is not whistleblowing, but a malicious attempt to smear the name of a hard working doctor. When allegations were made in 2011 we removed the doctor from performing interventional radiology procedures because of the seriousness of the accusations.

“Patient safety was and always will be our first priority, so we investigated the allegations, took the appropriate action and erred on the side of caution for our patients. However, with another independent investigation complete and the doctor exonerated, we are now convinced that these letters are malicious.

“We would advise any member of staff or patient to contact us in the first instance if they have any concerns about patient care and safety so they can be properly investigated. I would ask whoever is sending these distressing letters to patients to stop immediately, or to contact me directly to discuss their concerns.”

Staffordshire Police said in a statement: “We can confirm we have now received correspondence from the University Hospital of North Staffordshire. We will consider the information given to us to decide the appropriate way forward.”