The fiance of a Johannesburg advocate who was dragged for 700m behind a taxi yesterday, has been accused of assaulting the driver.

Kim McCusker, 25, is in a critical condition in the intensive care unit of the Life Fourways Hospital.

Her fiance, Lawrence Grobler, filed a complaint of assault against the taxi driver.

McCusker's family has filed a complaint in which the taxi driver is accused of attempted murder.

Police have charged the taxi driver with reckless and negligent driving.

McCusker was knocked down by a taxi in Lonehill, Johannesburg, yesterday morning after an altercation between Grobler and the taxi driver.

Grobler and McCusker were on their way to the gym when they almost collided with the taxi at about 6.30am on Lonehill Boulevard.

Martha Morudu, who was travelling in the taxi, said Grobler got out of his bakkie to confront the driver.

"[The taxi driver] nearly bumped his car," said Morudu.

"[Grobler] said to the driver, 'You nearly bumped my car.'

"He [Grobler] broke the window and hit the taxi driver," Morudu said.

The taxi driver was "fighting with her man" and "did not see the lady [McCusker]" who "came out from the car and stood in front of the taxi," said Morudu.

She said that when the taxi pulled off, the driver had probably not noticed where McCusker was standing because Grobler "was making a lot of noise".

Security guards witnessed McCusker being dragged for about 700m under the taxi.

Grobler got back into his bakkie and raced after the taxi to stop it.

A security guard, who asked that he not be named, said: "I saw the lady behind the car, just like a rag doll.

"I said: 'What is that?' and my friend said 'It's a human being'."

The guard said McCusker was covered in blood. Grobler, who had raced after the taxi in his own car, knelt beside his fiancee trying to see if she was alright.

McCusker was rushed to hospital by paramedics.

ER24 spokesman Derrick Banks said McCusker had multiple burns and abrasions across her body and possible fractures.

The McCusker family said they were in shock, and they didn't want to comment further.

Police spokesman Warrant Officer Balan Muthan confirmed that the driver had been charged with reckless and negligent driving.

"There are many charges that could follow," Muthan said.