Continuing his tirade against the prime minister, Dr Mahathir Mohamad said Najib Abdul Razak lives in the lap of luxury unlike his father Abul Razak Hussein.

The former premier also accused Najib of dishing out a "slew of lies".

"As prime minister, we should not lead luxurious lives. When Najib's father was prime minister, he used to cycle to the kampung.

"I too used to take my wife to the villages and there was once, I fell into the paddy field. That was how we led (the nation)," he said during his speech in Ipoh organised by the Gopeng Umno division today.

Mahathir claimed that Najib has been peddling lies, especially concerning the purchase of a new government jet.

Amid laughter, he pointed out while Najib possessed the "style of a leader", the many controversial issues surrounding him rendered the son of the second prime minister unqualified to hold the top post.

"(Najib) Never speaks the truth, always lies. How to be a leader?

"Yes, he is handsome, tall and fair. His hair is also white. The style is there and that is why I picked him back then (to be prime minister),"  he said.

Mahathir again reiterated that if Najib continued to helm Umno and BN, the ruling coalition would be defeated in the next polls due by 2018.

"If Najib is allowed to lead, he will lose (in the elections) and nobody will be able to provide us with protection. So it is better that he leaves before he loses," he stressed.

Najib: If I were a rich man...

Meanwhile, at a separate function in Klang, Najib continued to defend the debt-laden 1Malaysia Development Berhad (1MDB), describing it as a "goldmine".

1MDB tops Mahathir's list of grouses against the prime minister and also serves as one of the most potent weapons in the opposition's arsenal.

Even those in Umno have expressed concern about the firm's debts and questionable transactions.

However, Najib denied claims that a substantial amount of 1MDB's RM42 billion debt is unaccounted for, arguing that it is locked in the value of the firm's two major development projects.

"They say RM42 billion disappeared... It did not disappear. Look at the Tun Razak Exchange, there are 70 acres. Bandar Malaysia has 500 acres," he said in his speech at a gathering organised by former Umno elected representatives.

"This is a goldmine. If I were a rich man, I would buy there because I know its value after 20 years," he was quoted as saying by Malay Mail Online .