The charges were withdrawn by the Johannesburg Magistrate's Court.

"Solidarity will investigate the possibility of laying a charge of malicious prosecution against Madikizela-Mandela's bodyguard Jacob Monare," the union's spokesman Dirk Hermann said.

The altercation happened in 2010 when Warrant Officer Jannie Odendaal and Constable Abel Twala stopped Madikizela-Mandela's car because it was reportedly being driven recklessly at 150 km/h.

An argument ensued. Madikizela-Mandela's bodyguards brought charges of pointing of a firearm and intimidation against the policemen. They were suspended with full benefits.

Hermann said the initial charges against Madikizela-Mandela and her bodyguards should be re-investigated.

Charges of obstruction of justice against Madikizela-Mandela, and of assault and reckless or negligent driving against Monare and the driver were dropped by the National Prosecuting Authority (NPA), said Hermann.

"The NPA dropped the charges against them in 2011, while Odendaal and Twala were prosecuted," he said.

The two policemen had appeared in court on numerous occasions, but the case was postponed because the docket was not available. The senior State prosecutor decided to withdraw the charges against them on Wednesday.

"We are now investigating the possibility of charging Monare with malicious prosecution because of the possibility of political interference," said Hermann.

The NPA in Johannesburg could not be reached for comment on Wednesday.