The Mental Health Department has ordered an enquiry into comments allegedly made by Dr Kasem Tantiplacheewa, a psychiatrist at Somdej Chao Phraya Hospital.

He reportedly described caretaker premier Thaksin Shinawatra as mentally unstable during a recent debate organised by Chulalongkorn University. Dr Kasem was also quoted as saying the prime minister's mental state posed a problem for the country.

Department director-general ML Dr Somchai Chakrabhand warned that if the probe confirmed what was attributed to Kasem in news reports, the doctor would face further action.

Somchai denied Thaksin, Public Health Minister Pinij Charusombat or his deputy Anutin Charnveerakul were behind the order.

Chulalongkorn University lecturer Anan Lao-lertworakul, who invited Kasem to last week's debate, slammed the investigation. "It's abuse of power. It's unacceptable. This shows how unethical this leader is," Anan said, without using names.