Former premier Dr Mahathir Mohamad said it is up to suspended Umno number two Muhyiddin Yassin to decide if he wants to contest for the party president's post.

"He's still a member of Umno. He can challenge but it's up to him.

"If he wants to challenge, then by all means," he told reporters after attending an event at the Proton headquarters in Shah Alam.

Mahathir was asked if he would use his influence to urge Muhyiddin to take on Prime Minister Najib Abdul Razak in the next Umno polls.

When pressed, Mahathir reiterated: "It is not the case of me wanting, it's up to him. "

Ousted from the deputy prime minister’s post last year, Muhyiddin was suspended last Friday by the Umno supreme council for repeatedly speaking out publicly against Najib, who is also the party's president.

Yesterday, Mahathir, who had led Umno for more than two decades, quit the party in protest against Najib’s leadership.

He also called for Muhyiddin to follow in his footsteps and quit Umno.

Muhyiddin returns to Malaysia today after an overseas trip, and all eyes are on his next move.

When asked today if he would set up a new party or consider joining the Opposition, Mahathir reiterated he would not.

He said he would consider rejoining Umno if Najib leaves.

"I subscribe only to the struggle of Umno. But now Umno only fights for Najib, as if it is a political party for Najib.

"If Najib is not there, I will consider coming back," he said.

This is the second time Mahathir and his wife quit the party to protest against a sitting prime minister.

The couple previously quit Umno in 2008 to protest Abdullah Ahmad Badawi's leadership but rejoined when Abdullah stepped down in 2009.