Mr Leavers, who said he had not seen the footage, said anyone who spat or bit police officers could expect force to be used.

"[If] you spit in my face, you may very well get a punch in the face, absolutely," he said.

"I know when I've had people spit in my face it is a degrading act.

"And it's one of those things. [Retaliation] can become an instant reaction."

Mr Leavers said he did not condone violence but said police "were not robots".