Dr Mahathir Mohamad has accused Umno leaders and members of being "dumb, deaf and blind" in their support of Prime Minister Najib Abdul Razak.

The former prime minister said this led to him join hands with opposition leaders, such as DAP stalwart Lim Kit Siang, a collaboration that has drawn flak from Umno.

Acknowledging that Lim and he are political rivals, the nonagenarian said a common goal brought them together.

"Today, most Umno leaders and members have become dumb, deaf and blind. They know Najib's faults but still support him. Whatever wrongs Najib has done, they still support (him).

"This is no longer Umno. Don’t pretend to be an Umno member who is upset seeing me with Kit Siang.

"The ones who do not love Umno are those playing dumb, deaf and blind, when everyone is fed with animal feed (dedak)," he lashed out in his blog post.

Mahathir said it was Umno's responsibility to keep Najib in check but it had failed to do so, therefore forcing him to seek external assistance.

He said Najib's alleged transgressions went beyond the RM2.6 billion political donation he is said to have received from a Saudi royal member.

Najib, he added, failed to protect national assets by selling state land cheap to 1MDB, which later resold it for a mint to Tabung Haji, while burdening citizens with the goods and services tax.

"He shamed Malaysia. We are now among the 10 most corrupt countries in the world. He is condemned internationally. Is this the leader you support and defend?" Mahathir asked.

"The people hate seeing Umno members support Najib more than they despise seeing Umno members sit on the same stage as Kit Siang to topple Najib.

"At least we're not being fed by anyone," he added.