Calls for Economic Freedom Fighters leader Julius Malema to return to the African National Congress are desperate, President Jacob Zuma's son, Edward, said on Wednesday.
"It is my plea not to suck up to this call, and totally reject it regardless of who raised it," Zuma said.
Malema was a "reject and disrespectful thug".
Mpumalanga Premier David Mabuza said on Sunday that the ANC was weaker without Malema. He said he was considering bringing him back to the party that expelled him.
On Tuesday, ANC Youth League president Collen Maine said he supported calls for former members, including those in Cope and the Independent Democrats, to return to the party if it would make the ANC strong again.
Edward Zuma said the party should not accept Malema back based on his popularity. He needed to return of his own volition and adhere to the party's rules and respect its constitution and leadership unconditionally.
Malema, a former ANCYL president, was expelled from the party after a disciplinary inquiry found him guilty of offences, including unfavourably comparing Zuma to his predecessor Thabo Mbeki.
Mabuza and Maine are staunch supporters of President Zuma. Zuma junior's open criticism of Malema was likely to raise eyebrows.
"We cannot agree with those of our leadership that are making such a call, based on being afraid of what 2019 is bringing for us comrades, or whatever their fears might be. We as members aren't scared and are prepared to defend and build this ANC without rejects like Malema."
The EFF on Monday dismissed Mabuza's calls for Malema to go back to the ANC. The party accused Mabuza, who is also the ANC's provincial chair, of using Malema's name to gain traction for his own campaign in the ANC's elective conference in December.
Some ANC members want Mabuza to get a top six position.