In mobile phone footage posted on Twitter two men can be seen punching and kicking the male and female officer as scores of people pass without intervening.
The shocking incident in Merton, south west London on Saturday night, saw the two male attackers wearing hoodies and dragging the policeman away from his patrol car and kicking him.
A policewoman can then be seen trying to pull them off her colleague but she fails as a man brutally kicks her to the ground.
The assault comes amid London’s violent crimewave, with the capital’s murder count reaching 122 so far this year over the weekend.
The clip, recorded by a man in his car at 7.55pm on Saturday with music playing in the background, shows several people walk by without stopping to help the officers.
A bus also drives straight past the chaos without stopping to intervene.
Eventually, with the help of a heroic moped rider, the policeman manages to get the attacker off him and pins him down ready to arrest him.
The video was uploaded to Twitter alongside the caption: ‘South London at night.. Lol’.
A Met Police spokesman told MailOnline a 20-year-old man was arrested and charged with causing ABH and assaulting an emergency services worker.
He was also charged with driving without a licence or insurance after being stopped by police. He will appear at Wimbledon Magistrates Court today.
Two other men involved, one of which is seen in the video footage, are still at large.
The footage received a mixed response on Twitter, with some finding it funny and others slamming the witness for not intervening.
‘Not even the slightest bit funny. If it was the other way round, there’d be riots in the streets lol. Have some respect,’ one person tweeted.
Another said: ‘Shame on you for filming this and not trying to help.’
And one user commented: ‘ How people can find this funny is beyond me….. and to film it and not even bother to help!!
‘These people would be the first to ask for services when needed!’
Police numbers have been called into question after the number of stabbings and shootings across London spiralled out of control.
The latest fatal stabbing took place in Peckham, south east London, claiming the life of pensioner Maureen Watkins, 75.
Her son, Edward Watkins, 55, has been charged with her murder.
In a horrifying attack last week, a mother-of-five from Ilford, east London was killed after being shot with a crossbow in front of her children.
Ramanodge Unmathallegadoo has been charged with Sana Muhammad’s murder, which also saw her unborn baby delivered by emergency C-section after she was shot in the stomach.