- Explosive new claims allege PNG PM's corruption
- PNG prime minister says fraud allegations 'politically motivated'
A warrant for Mr O'Neill's arrest was obtained on Monday by fraud investigators who want to grill the prime minister over allegations he siphoned millions of dollars of public cash to a law firm.
Mr O'Neill strongly denies any wrongdoing and obtained a court order putting the warrant on ice.
The key evidence in the case - which has gripped PNG for months - is a letter that Mr O'Neill allegedly signed authorising $31 million be paid to prominent law firm, Paul Paraka lawyers.
The prime minister has dismissed the note as a fake.
But Taskforce Sweep boss Sam Koim revealed on Tuesday that Sydney-based private investigators believe the document is genuine.
"We have now received the forensic examination report from the Sydney-based Forensic Document Services Pty Ltd confirming that the signature on the letter ... directing payments to Paraka Lawyers is PM O'Neill's," Mr Koim said.
Police Chief of Operations and Deputy Commissioner Simon Kauba said his officers would abide by Monday's court ruling that stayed the warrant for Mr O'Neill's arrest.
But he urged the prime minister to hand himself in.
"In the interest of national security I would like to invite the prime minister to, without any further delays, voluntarily make himself available to police for the interview to be conducted," Mr Kauba said.
The case will be back in PNG's National Court on Wednesday morning, with Mr O'Neill's lawyers due to respond to an affidavit filed by Mr Koim on behalf of Task Force Sweep and the police.
Meanwhile, Mr O'Neill has announced a commission of inquiry into the allegations against him - led by Australian judge Warwick Andrew.
Mr O'Neill claims that police, courts and government departments have all been politically compromised.
"I think it's needed to be cleaned and we need an independent process to clean it out," he added.
The Paul Paraka affair - called Parakagate in Port Moresby - is one of PNG's longest-running fraud investigations. Mr Paraka, one of the most powerful lawyers in PNG, was arrested and charged in 2013 for allegedly receiving the state monies.
Task Force Sweep alleges the payments were spread over a seven-year period and ran into the "hundreds of millions".
