UPDATED 5:10pm: The Health Minister is seeking assurances as a former Waikato District Health Board psychiatrist has been accused of identity fraud.

A health board staffer working as a psychiatrist was been fired and arrested for possible identity fraud, sparking concerns for dozens of vulnerable patients he saw.

Minister Dr Jonathan Coleman says his first action has been to seek assurances over patient safety.

He says he's also seeking assurances over the recruitment process followed by the Health Board and the Medical Council.

Dr Coleman is meeting with the Director General of Health tomorrow to discuss the matter. 

Waikato District Health Board (DHB) said it had identified "serious issues of potential identity fraud" and a man who'd been working as a consultant psychiatrist appeared in court yesterday on a fraud charge.

The man's patients included people with mental health and addiction issues.

The man was under the supervision of a senior psychiatrist while working at the DHB but he saw some patients without supervision.

"The supervisor raised concerns about their professional ability, ultimately withdrawing supervision, which resulted in immediate withdrawal of the person's ability to practise," Waikato DHB chief executive Dr Nigel Murray said.

Waikato DHB said it was now contacting about 25 patients the man saw during his roughly six-month tenure at the health board.

The DHB said it and the Medical Council of New Zealand identified concerns about the documents the man presented -- which may have belonged to someone else.

"As these enquiries raised serious issues of potential identity fraud, this person is no longer employed by the Waikato District Health Board and is unable to carry out medical duties in New Zealand," the DHB said today.

The man was given name suppression at Hamilton District Court yesterday and remanded in custody.

The man worked in the crisis, triage and home-based treatment services between January 19 and July 17.

"These services are responsible for triaging all contacts with mental health services and directing them to the service best placed to meet their needs. This person worked within a multi-disciplinary context and usually saw patients in the company of another member of staff," the DHB said.

"We are extremely concerned and our first priority is for the safety of our patients and their families. The information to date has not identified any harm to patients and we will continue to assess the situation" Dr Murray said.

"Whilst most patients seen by this person have subsequently been reviewed and are receiving appropriate care and treatment we have identified approximately 25 patients who have not been further followed up," he added. "Each patient will be offered follow-up services as soon as possible."

The health board said it carried out checks on the man's credentials and information available to the DHB and the Medical Council "verified the person's qualifications and ability to practice in New Zealand."

Now, both organisations said they would review their systems to strengthen their ability to identify potential fraud.

The father of a man who died under the care of Waikato Hospital's mental health unit says the court case against a suspected fake psychiatrist shows the department is in crisis. 

Dave Macpherson said as a parent of a former patient, it's concerning to hear.

"It says that the management systems are in chaos or non-existent, or a combination of both. This is not the first time this sort of thing has happened." 

The DHB said patients seen by the triage, crisis or home-based treatment teams during this time who had concerns should call the Triage Service 0800 50 50 50 or email [email protected].