The Jacob Zuma Foundation is once again attacking Deputy Chief Justice Raymond Zondo.
It comes as the Constitutional Court says it will hear the contempt case against the Former President on 25 March.
The foundation accuses Zondo of abusing his position as second in command of the Constitutional Court.
It says he is instructing his subordinates to bend the laws to ensure that Zuma is found guilty.
Zuma was summoned to answer to allegations that he enabled corruption during his tenure in office.
Zondo has asked the Constitutional Court for an urgent order to declare him in contempt of court and sentence him to two years in prison if found guilty.
The foundation says according to the law, the punishment should either be six months imprisonment or a fine.