Two more charges have been laid against a former psychiatrist at Cambridge Memorial Hospital.

In April 2012, a man came forward with allegations of sexual assault and exploitation against Allan Umar-Khitab. Charges were laid in that incident, which is alleged to have happened in 1994, in August.

Police have since charged Umar-Khitab, 74, with further counts of sexual assault and sexual interference.

Police say the new incident, in which the psychiatrist allegedly sexually assaulted a patient, happened in the early 1990s.

The complainant is the sixth to come forward with allegations against Umar-Khitab, but police say is not connected to any of the other cases.

"In this particular case, a victim did come forward and contact police in the last few months," says police spokesperson Olaf Heinzel.

"As a result of the information brought to us, we conducted an investigation and that resulted in the charges being laid."

In 1999, Umar-Khatib was accused of molesting five boys, aged 12 to 15, who were his patients between 1989 and 1994. Two years later, he pled guilty to professional misconduct and lost his psychiatry license.

Police say the latest alleged victim to come forward was younger than any of the previous victims.

Umar-Khitab was released from custody on a promise to appear and is scheduled to appear in Cambridge court on Thursday.