Hanipa, the de facto deputy law minister, said Najib’s plan to take a “sumpah laknat” tomorrow had little legal value.

“You are not subject to any cross-examination,” he told FMT in a text message.

“Najib can file a defamation suit against his accuser if he believes that he is being defamed. It follows that he would then be subjected to cross-examination by the defendant’s lawyer.”

Najib said yesterday that he would take a religious oath at Masjid Jamek in Kampung Baru to deny the allegations by former police officer Azilah Hadri.

Azilah, in a sworn statement, claimed that the order to kill Altantuya came from Najib, who was deputy prime minister at the time.

However, Hanipa, a former lawyer, said taking an oath in a mosque was akin to “one-way traffic”.

Based on his experience in court, he added, cross-examination was the best way to expose lies.

“In my view, filing a civil suit against his accuser is the best option which he should take rather than swearing an oath on any day, at any place.”

Altantuya was murdered in October 2006 in the jungles of Puncak Alam near Shah Alam, Selangor. She was shot in the head before her body was blown up with explosives.

Her murder has been linked to the 2002 purchase of two French-built Scorpene-class submarines and alleged kickbacks to Abdul Razak Baginda, an aide to Najib when he was defence minister. Razak has denied this.

Najib has also repeatedly rejected allegations of his involvement in the crime.

Azilah, a former Special Action Unit commando, recently filed a statutory declaration for a review of his murder conviction.

He and Sirul Azhar Umar, who was also convicted of Altantuya’s murder, were part of the police’s Unit Tindakan Khas at the time of their arrest.