Johannesburg - Imvume Investment (Pty) Ltd, a black economic empowerment firm, is suing the Freedom Front Plus for defamation, the party said on Tuesday.
Lawyers for Sandi Majali, Imvume's chief executive officer, have already given notice that they intend suing the FF+ for defamation, said Willie Spies, the party's spokesperson on minerals and energy.
"A defamation suit could just have the opposite effect as to what Imvume has in mind," he said in a statement.
Two months ago, Imvume obtained a court order gagging the Mail & Guardian newspaper for revealing that Imvume donated R11m to the African National Congress before last year's general elections.
The money was part of R15m Imvume received from PetroSA as an "advance" for oil condensate which came from Glencore.
Instead of paying the money to Glencore, Imvume allegedly paid it to the ANC as a donation. When Imvume did not pay Glencore, PetroSA allegedly had to duplicate the R15m payment to Glencore.
Imvume lifted the order against the Mail & Guardian after the FF+, using its parliamentary privilege, disclosed the details of the transaction.
"A defamation suit can only succeed if the particulars which had been revealed are incorrect and if it is not in the interest of the public to have the particulars made known.
"In this case we particularly wish that an independent forum such as one of the courts test the truthfulness of the allegations surrounding the Oilgate scandal and the public interest in this case speaks for itself - it is after all R15m of taxpayers' money which is in question," Spies said.
He said Imvume and Majali were central in the Oilgate scandal currently being investigated by the Public Protector.
"Imvume earlier also gave notice that it wants to force the FF+ in court to reveal its source.
"According to a letter from Imvume's lawyers, Barry Aaron and Associates, addressed to the legal team of the FF+, the court documents for the application regarding the revelation of the source of the FF+, will shortly be ready," he said.