Ezam Mohd Nor has left Parti Generasi Baru (NewGen) following frustrations over the delay by the Registrar of Societies (ROS) in having the party renamed as Parti Bebas Rasuah.

This is the fifth time Ezam has left a political party since 1998.

In a statement, Ezam also cited the "lack of positive indications" that NewGen's application to change amend its constitution would be approved by the ROS.

Ezam, who was NewGen's president, explained that changing the party's name was crucial because he and his party had the single goal of eradicating corruption.

"This (delay by the ROS) has made it difficult for us to move forward as a party that is specifically aimed at battling corruption."

"It halted our agenda of battling corruption which has put Malaysia in a critical state," he said.

His resignation letter to NewGen was dated June 1.

Ezam said his anti-corruption drive would continue through the Hisbah Centre for Reforms, an NGO which he leads.

For now, their immediate priority was to publish the latest edition of his book titled "Islam and the question of corruption".

"Hisbah is taking up the responsibility to explain Islamic principles that make acts like stealing national funds or kleptocracy haram (forbidden)," he said.

One chapter will focus specifically on 1MDB, he said.

Meanwhile, The Star Online reported that former Umno and Parti Pribumi Bersatu Malaysia member Khairuddin Abu Hassan has also quit NewGen party, effective June 1. 

Ezam was an up-and-coming Umno Youth leader in the late 1990s who left the party after his mentor Anwar Ibrahim was sacked as deputy prime minister.

He then founded PKR Youth and led the movement until his departure from the party in 2007 after an apparent fall-out with Anwar.

After spending time abroad, he resurfaced in mid-2008 by joining Umno.

He was appointed a senator in 2010 by the Najib administration.

He would then quit Umno and join Parti Pribumi Bersatu Malaysia (Bersatu) in 2016. He left Bersatu just after two months.