A motorist who headbutted an ambulance driver in a spat at Tan Tock Seng Hospital and used his forehead to push an accompanying nursing officer's forehead was given four months' jail.

Sim Kwang Wee, 53, admitted to causing hurt, pain and injury in using his forehead to hit Mr Thomas Charles, 64, on the forehead.

The incident happened on Dec 14, 2016, at the emergency ambulance drop-off point fronting the hospital's emergency department.

Sim also used his forehead to push the accompanying officer, Mr Charles Gabriel, 29. He did this because he was unhappy that Mr Gabriel had used his mobile phone to film him. This second charge was taken into consideration for sentencing.

Sim had assaulted the two men when they were trying to bring down an 82-year-old suspected stroke patient from the ambulance, noted District Judge Ng Peng Hong in decision grounds released late last month.

The rear door of the ambulance could not be opened because Sim's vehicle was in the way. The private-hire driver had earlier helped ferry a domestic worker for treatment at TTSH.

When Sim was asked to give way, he refused and the spat followed.

Mr Charles eventually drove to another drop-off point some 20m away. He later received outpatient treatment at the hospital.

Deputy Public Prosecutor Kong Kuek Foo called for a deterrent jail term, as the ambulance service workers were performing a critical public function and any violence against them cannot be condoned.

Sim's lawyer John Koh pleaded for leniency and urged the court to impose a fine, arguing that Sim lost his temper.

The judge noted Sim's "outrageous and despicable behaviour" and that the assault occurred at a public hospital in public view.

"It would cause alarm and disquiet to the public."

Sim is appealing the decision.