The former prime minister aged 90, former Batu Kawan Umno vice chief Datuk Seri Khairuddin Abu Hassan, 54, and former Langkawi Wanita Umno member Anina Saadudin, 41, had appealed against the High Court's decision to strike out their suit against Najib.
They sued Najib on March 23, 2016 and the prime minister subsequently filed an application on April 19 to strike it out.
On April 28, 2017 the High Court allowed Najib's application to strike out the suit, ruling that the prime minister was not a public officer but a member of the administration.
Today, a three-man bench led by Court of Appeal Judge Tan Sri Idrus Harun unanimously decided that Dr Mahathir, Khairuddin and Anina's appeal had no merit, and affirmed the high court's decision. The panel also awarded RM30,000 costs to Najib.
"We agree with the submission of counsel for the respondent (Najib) and we are satisfied that there are no merits in the appeal and therefore we dismiss the appeal," said Idrus who sat with Datuk Vernon Ong Lam Kiat and Datuk Abdul Rahman Sebli.
Earlier, counsel Mohamed Haniff Khatri Abdulla who represented the appellants submitted that there were serious issues to be tried on the cause of action of breach fiduciaries in public office by the respondent and that the ingredients of the tort of misfeasance had been fulfilled.
"The appellants are fit and proper parties to bring and maintain this action against the respondent and this is not a fit and proper case to be summarily struck out," he said.
He also argued that the high court judge had erroneously applied the wrong principles of law in defining the terms 'public office' and 'public officer', and failed to consider the appellants' claim.
Najib's counsel Tan Sri Cecil Abraham countered that as the appellants' claim was over tort of misfeasance in public office, they should have proved that the respondent was a public officer.
He contended that the prime minister was not a public officer but a member of the administration as defined under the Federal Constitution.
"It is clear that the respondent (Prime Minister or Minister of Finance) does not fall within the definition of 'public officer' to satisfy the ingredient of tort of misfeasance in public office," he stressed.