Mahathir said he was unhappy with Abdullah Badawi who took over from him for changing his mind not to build Johor Bharu - Padang Besar double track rail project and allowed his children to join the government meetings. He would just leave the party then and criticized Abdullah. 

“I did not only leave the party but also form a new party to oppose UMNO with Muhyiddin Yassin (former Deputy Prime Minister cum president of Parti Pribumi Bersatu Malaysia). In the past Tunku Abdul Rahman expelled me. I did not oppose UMNO. I left the party when Abdullah Badawi was the Prime Minister but this is the first time I set up a new political party,” Mahathir told Sin Chew Daily at his office in Putrajaya.

He said Parti Pribumi Bersatu Malaysia founded by him is a Malay-based political party and different from the multi-ethnicity of Parti Keadilan Rakyat and Parti Amanah Negara. Rural voters are fearful of multi-racial political parties. 

“As a Malay political party, it is easier for UMNO party members and supporters to accept us in rural areas," he said.

The opposition achieved breakthrough in May 5, 2013 election which won 52 percemt of votes but still lost to Barisan Nasional. Mahathir said opposition would need 20 to 30 more seats to be ruling government.

“The opposition would need our participation to secure enough seats. I think we can deliver and we are only targeting against UMNO,” he added.

Mahathir stressed that even if Najib were to step down after the general election, he would not return to UMNO. Pribumi would not form joint government with UMNO even without Najib or carry out any political collaboration.

“No. We can’t. The problem is not Najib only,” he said. "They [UMNO] are completely corrupted. I am unable to accept this. I can’t return.”

“In terms of performance, ideology and operating style, it is no longer UMNO. So I would not return.”