Mukhriz Mahathir disagrees with the police closing the file on a report alleging a high-level conspiracy against Prime Minister Najib Abdul Razak.

In a text message to Malaysiakini, the former Kedah menteri besar said when the vice-chief of Umno Youth made such a serious allegation, he must have had justification for it.

Quizzed on the claims that the alleged conspiracy was masterminded by his father, Dr Mahathir Mohamad, Mukhriz once again underscored the importance of an exhaustive probe.

"Again, that's for the police to investigate.

"How can PDRM (police) dismiss it (allegations in the report) as mere hearsay?" he added.

Last week, Umno Youth vice-chief Khairul Azwan Harun caused a stir by filing a police report naming former Bank Negara governor Zeti Akhtar Aziz, former attorney-general Abdul Gani Patail and former Malaysian Anti-Corruption Commission (MACC) chief commissioner Abu Kassim Mohamed of being involved in a conspiracy against Najib.

He accused the trio of submitting classified information to foreign agencies, including the Federal Bureau of Investigation (FBI), without authorisation.

Khairul also claimed that the three falsified information for their agenda.

However, inspector-general of police Khalid Abu Bakar ruled out an investigation, saying that it was found that Khairul, upon being questioned, based his report on “assumptions and hearsay”.

He also dismissed the need to probe the Umno Youth leader for making a false report.

Strangely, Khairul viewed the episode as a success, claiming that the police report had foiled the alleged plot.

Meanwhile, blogger Raja Petra Kamaruddin also weighed in on the matter, claiming that the three former high-ranking officials must have breathed a sigh of relief with the police's decision since a probe could have proven disastrous for them.

Raja Petra also alleged that since Mahathir had "all their files", the three had no other choice but to do the former prime minister's bidding.

"It is because Mahathir had his gun to their heads," he stated in his website Malaysia Today.

Of the three, only Gani had responded to the police report, describing it as nothing more than a publicity stunt.

Zeti had told the media she was seeking legal counsel while Abu Kassim said his lawyer instructed him to remain silent.

Najib himself has repeatedly alleged the existence of a conspiracy to topple him from power and pointed his finger at Mahathir.