Late Malaysian premier Mahathir Mohamad said he is quitting the party he led for more than two decades, increasing the stakes in his months long campaign to oust Prime Minister Najib Razak due to some issues that is happening.

Mahathir, 90, said the United Malays National Organization (UMNO)he largest party in the ruling coalition,no longer exists as he knows it and has been “hijacked” by Najib, who is its president. Mahathir told reporters on Monday that he doesn’t want to be associated with a party whose leader has been tarnished by political scandals.

Mahathir, whose influence has waned in recent years, has a history of leaving the party since the late 1960s. He’s been a vocal critic of Najib and has repeatedly called for the premier to resign, warning UMNO could otherwise lose the next election, which must be held by 2018.

Malaysia’s attorney general closed the door on a graft probe of Najib in January, clearing him of wrongdoing over a “personal contribution” of $681 million from Saudi Arabia’s royal family and money that appeared in his personal bank accounts but still Najib has consistently denied any wrongdoing.