Anwar, seeking a return to active politics after nearly 10 years, is one of three candidates vying for the presidency of Parti Keadilan Rakyat.
On Friday the Registrar of Societies rejected his bid to run in the polls, upholding the ban that was imposed in 2003 following his conviction for corruption.
The ban runs until April 2008. Anwar has since appealed to Malaysia's home minister, who has the right to grant a waiver, against the decision, Chua said.
The current party chief is Anwar's wife, Wan Azizah Wan Ismail, who is also running for the presidency, said to be largely a precautionary move in case authorities disqualify Anwar.
Anwar, a former deputy premier, was charged with both corruption and sodomy in 1998, days after he fell out with Mahathir Mohamad, his boss and Malaysia's then president, calling for political reforms and heading a campaign of protest that culminated in a popular "Reformasi" movement.
Malaysian law bans criminals from holding public office for five years after their release from jail.
Anwar had effectively served his corruption sentence in April 2003, but remained in jail until acquitted of sodomy in 2004.