Speaking to reporters here today, the deputy prime minister also stressed that the party's disciplinary board which found Mohd Ali guilty of campaign offences was independent and should not be questioned.

"If we begin questioning the integrity of the disciplinary board, there will be many unhealthy implications," said Najib.

On the question of whether the Melaka chief minister was made a scapegoat in Umno's bid to clean up the party, Najib said: "No, Ali Rustam is not a scapegoat; this is not the case."

"Neither is he a victim of sabotage because the disciplinary board had acted based on complaints," he added.

Mohd Ali was barred from contesting in next week's party polls after being found guilty of breaching party ethics on Tuesday. Three of his "agents", including his political secretary, were found guilty of breaching the party's anti-money politics rules.

Mohd Ali was found guilty under Article 10.1 of the party's code of ethics, whereby he was presumed guilty by association for the actions of lobbyists or agents.

"Umno must make a firm stand. If not, all sorts of activities will take place in a bid to grab positions in the party. We cannot compromise and have to place our trust in the board," said Najib after launching the Inland Revenue Board's electronic services.

"In any case, he has the right to appeal and we cannot deny his right. Whether he is successful or not depends on the panel's discretion," said Najib.

Najib also said the disciplinary board could only investigate those against whom complaints were made.

Commenting on why certain party members were being investigated by the Malaysian Anti-Corruption Commission but not the disciplinary board, Najib said: "Sometimes, we think that certain individuals have indulged in misdeeds but there is no proof.

"As such, the disciplinary board can only act on the evidence presented to them."

Pending the hearing of Mohd Ali's appeal, the Bukit Katil division head will remain as Melaka chief minister and continue to head Umno's by-election machinery in Kuala Sepetang.

Kuala Sepetang is one of three state seats under the Bukit Gantang parliamentary constituency in Perak. Nominations for the Bukit Gantang by-election will be held on March 29 and polling on April 7.