AfriForum's head of private prosecutions, Gerrie Nel, has filed a mandamus application against the South African justice ministry to force it to accede to a request from Botswana for mutual legal assistance in a money-laundering case allegedly involving president Cyril Ramaphosa's sister-in-law, Bridgitte Motsepe-Radebe.

Nel on Thursday told the media the application was filed after the department of justice failed for 11 months to respond to the formal request from Botswana's director of public prosecutions, Stephen Tirayakgosi, for help on the matter.

He added that South Africa's failure to respond was stalling the legal process in its northern neighbour, and ventured that at most it should have taken the state three months to render the requested assistance.

To date, there has been no response from the department of justice.

"The matter was on the court roll this week and had to be postponed again because of the fact that the information requested was not provided. Now if you prejudice an investigation and you do so deliberately then it is tantamount to defeating the ends of justice," Nel told a media briefing.

"We have filed our papers, failure to respond to our papers, failure to provide the information, we will have to go through the application and then let the court then direct a response from the department of justice."

The press conference came one day after a report commissioned by Motsepe-Radebe from international law firm Omnia Strategy was released.

The report dismissed allegations that Motsepe-Radebe was the signatories to two bank accounts holding US$10-billion that was stolen from the Bank of Botswana to finance a conspiracy by former Botswana president Ian Khama against his successor, President Mokwetsi Masisi.

Asked about the report, Nel said his brief was not to delve into the merits of the case but merely to ensure that the government cooperated with authorities in Botswana.

He has not given the specifics of the cooperation Botswana is requesting and said he has not included it in court papers either, but believed for an investigation to be fair, all information should be availed.

"I would not like to discuss the merits of the mutual legal assistance request .... my brief is just to ensure that the department of justice provide the information requested."

He added though that he was obviously familiar with the nature of the request, and believed the information sought might also be useful for those who compiled a report at Motsepe-Radebe's request.

"You need all the information involved in an investigation," the former senior state prosecutor said.