A judge has blasted the NSW police system and accused an officer of 'appalling' behaviour after he pointed his gun at an innocent driver during a roadside breath test.

An internal investigation conducted by NSW Highway Patrol in 2016 cleared the officer of wrongdoing, but he has since come under fire amid a separate investigation.

Police watchdog Law Enforcement Conduct Commission (LECC) released a report on June 26 stating the investigation's findings 'were not reasonably available in light of the evidence.'

In dramatic dashcam footage the officer is seen pulling over the suspected drunk driver just outside of Canberra on January 22, 2015.

Dramatic footage has emerged of a NSW Police highway patrol officer pulling his gun on a man

The actions of the cop were heavily criticised by a magistrate who said she was 'appalled' by them

The video shows the officer running to the door of the car with his gun pointed at the driver, before flinging the door open as the man emerges with his hands up.

With the service pistol pointed at the man's head, the police officer then appears to tell the driver to get down onto the ground and put his hands behind his back, and the man complies.

The officer then holsters his gun and knees him in the back and punches him in the neck while handcuffing the man, who had a positive blood-alcohol reading.

The driver was charged with drunk driving but the offence was later dropped after it was revealed the device used to carry out the test was not an approved breathalyser.

The officer's actions were heavily criticised by a magistrate in 2016 who said she was 'appalled' by the policeman's response.

During a hearing at ACT court Special Magistrate Margaret Hunter said it had been 'clearly unnecessary' for the officer to draw his gun and point it at the man's face.

'I was horrified when I heard in cross-examination by him that he'd actually taken his gun out of his holster. I mean, that's not something Australian police do. Very rarely, in fact, I was under the impression that if they even took the snap lock of the holster off they had to report it,' she is quoted in new documents.

The officer was seen holstering his gun and knees him in the back and punches him in the neck while handcuffing the man, who had a positive blood-alcohol reading

She goes on to say: '....I was quite distressed to see the action that he did in the man's back. I mean, was that necessary? He says it was but I don't see why.'

'...What I'm saying is that this officer's behaviour was extraordinary and quite offensive, in my view, and whether it was unnecessary that's something I'm going to have to think about.'

However, the new LECC report revealed the complaints against the officer, including unnecessary use of force and unnecessary use of a weapon, among others, were 'not sustained.'