It appears that his two-month prison stint had failed to break Khairuddin Abu Hassan's spirit, as he continues to pour scorn on Prime Minister Najib Abdul Razak and his supporters.

In a Facebook posting riddled with insults and exclamation marks, he criticised the move to prevent deputy president Muhyiddin Yassin from addressing delegates at the Umno general assembly next week.

"As a former division vice-chief, I am most embarrassed with the present Umno leadership who lead the party as if it belongs to their father," he said.

Khairuddin questioned until when would the leadership continue to fool the members, and lambasted those who sit on the supreme council as "kaki bodek" (apple polishers), "minda lemah" (weak minded) and "otak udang" (stupid).

The former Batu Kawan Umno vice-chief called on all Umno members to vehemently oppose the supreme council's decision, which is unfair to Muhyiddin.

"Umno is increasingly becoming a 'gila babi' (mad) party.

"This is a clear sign that the 'kaki bodek', 'minda lemah', 'otak udang' who sit on the supreme council are among those who are ruining the party.

"We should not be afraid of these 'bangang' (idiots). All their stupid decisions must be opposed. This is crucial to safeguard the future of the party we love," he added.

Khairuddin, who is currently on bail, said he often prays that the supreme council is booted out because they are not qualified to lead.

"Every Umno member at the grassroots level should not give them a single vote when the party election comes if you want Umno to remain relevant," he added.

Khairuddin and his lawyer Matthias Chang were arrested under the charge of sabotaging the Malaysian economy after filing a slew of reports against 1MDB in several countries.

During an exclusive interview with Malaysiakini , the Umno man denied he was acting on the instructions of Dr Mahathir Mohamad, who is pushing for Najib to step down.

Khairuddin had also described the prime minister as being "thick skinned".