Prime Minister Dr Mahathir Mohamad reacts more fiercely when he is challenged, said Kedah Menteri Besar Mukhriz Mahathir, who is also his son.
Mukhriz said this in reference to attacks on Mahathir's government after Putrajaya decided not to ratify the Rome Statute.
"Who does not know Mahathir? He is a person who does not like to be challenged. When he is challenged, he becomes stronger and fiercer (hebat dan garang)," he was quoted as saying by Berita Harian.
On Friday, Mahathir announced that the government was withdrawing from the Rome Statute due to the confusion created by "one particular person who wants to be free to beat up people".
Mahathir said there was also an attempt to get the rulers to sign an order against him.
PKR president Anwar Ibrahim later revealed that the person referred to was a "particular personality from a royal family".
Mukhriz said as a son and a Pakatan Harapan leader, he will continue to support Mahathir on the issue.
He added that his father has a strong will and is unfazed by the moves against him.
Among the strongest critic of the Rome Statute was Johor crown prince Tunku Ismail Sultan Ibrahim.
Tunku Ismail claimed that the Rome Statute, which governs the International Criminal Court – that only deals with genocide, crimes against humanity, war crimes, and the crime of aggression – would threaten the position of the Yang di-Pertuan Agong, Malays and Islam.