Since launching a series of attacks against Najib Abdul Razak, Dr Mahathir Mohamad has for the first time roped in the prime minister's wife Rosmah Mansor.

"There are many things about his (Najib's) personal behaviour that I thought were not right.

"But I was prepared to overlook them, including his and his wife's lavish lifestyles," Mahathir said in his latest blog post.

Rosmah has often been accused of being a spendthrift with a penchant for luxury goods, an issue which even made news in the New York Times .

When the Prime Minister's Office attributed Najib and his family's lavish expenditure to inheritance, it prompted the prime minister's brothers to issue a statement on how their father's reputation was being tainted and pointed out that the late Abdul Razak Hussein was a frugal man.

Next change: Dr M on 1MDB

Apart from being a target for the opposition, Rosmah was also speculated of causing a rift between Najib and his siblings, which has been denied.

Meanwhile, Mahathir said he could no longer ignore Najib's actions after the 1Malaysia Development Bhd (1MDB) issue.

"When he cannot explain where billions of ringgit have gone to and his involvement with questionable people in the management of 1MDB, I felt that he is not fit to be the prime minister of this country," he added.

The former prime minister said he would explain how Najib lost billions of ringgit in his next blog post.

Not because of bridge

Meanwhile, Mahathir explained that the reason why he is seeking Najib's ouster had nothing to do with the latter's decision not to revive the "crooked bridge" project.

Describing it as a "shameful episode", because Malaysia refused to build the bridge on its own land without Singapore's approval, Mahathir said it was not good enough a reason to ask Najib to step down.

"I am not so frivolous," he said.

Instead, Mahathir said, some of these mega-projects were important for the country and could have saved the money of taxpayers.

Citing the example of the double tracking project from Johor Bahru to Padang Besar, he said it would have been completed by 2010 for RM14 billion.

"Instead, forced by the demand, (the Abdullah Ahmad Badawi administration) sanctioned the continuation of the track from Ipoh to Padang Besar for RM12 billion. We lost a lot of money."

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