The new public protector says she will leave the dispute over the state capture report prepared by h.
The IFP has accused the South African Human Rights Commission of having lost its "credibility and denting its image".
The party said the commission (SAHRC) had held a "secret" meeting with ANCYL president Julius Malema and senior leaders of the ANC.
Velaphi Ndlovu, IFP safety and security spokesman, said the human rights body owed citizens an explanation on why, after Malema did not meet the 14-day deadline to apologise or retract his "kill for Zuma" statement, the parties had met secretly.
Ndlovu said: "They have decided not to take further legal steps against him. How can this be? As far as we can establish there was no apology or retraction from Malema.
"This is very disheartening. We are amazed at how the SAHRC does business. How could they go back on their word when they made such a public noise about Malema's statements?" Ndlovu asked.
The SAHRC's chief executive, Tseliso Thipanyane, denied that it had met the ANC or Malema secretly, and said the IFP was welcome to raise its concern with the commission or Parliament.
"We have dealt with many people whose utterances threatened our democracy. We were the first to ask Irvin Khoza to apologise about his use of the word 'kaffir', but he did not just apologise. We resolved the issue without going to the equality court," Thipanyane said.
He said the SAHRC had followed the correct channels regarding Malema. It had two meetings - one with the ANC national executive committee and another with Malema.
"We met the NEC for about two hours. We were not pleased. Then Malema came to us with Winnie Madikizela-Mandela and he put his signature to the press statement after a one-hour meeting. He agreed not to use the world kill in the future," Thipanyane said.