Deputy communications minister Stella Ndabeni is planning legal action against ANC Youth League spokesperson Magdalene Moonsamy and other league members over the release of a letter, the Star reported on Wednesday.
The letter criticises Ndabeni for remarks she made about Winnie Madikizela-Mandela, the ex-wife of former president Nelson Mandela.
Ndabeni's lawyer, Makhetha Matumba, said the charges were crimen injuria and defamation of character.
"We are suing all those people on the letter, including Magdalene," she told the newspaper.
The names of eight league members appear at the bottom of the letter.
The matter relates to Ndabeni's Facebook post about Madikizela-Mandela's criticism of President Jacob Zuma's polygamous lifestyle.
Ndabeni wrote: "Life can be interesting. Dali Mpofu represented Julius Malema in the national disciplinary committee hearings, Mam' Winnie has always seen a great leader like Madiba in Malema, and now the mother of our nation sees immorality in Zuma. Who is a saint between the two of them?"
Moonsamy responded by writing an open letter to Ndabeni, attacking her for criticising Madikizela-Mandela.
She, however, denied she had anything to do with a second letter, which is now the subject of the defeamation charge.