A controversial New Zealander is a fantasist who likes to play at being James Bond, a President's personal lawyer and the arresting officer of terror suspects in the Rainbow Warrior bombing, a Hong Kong court has heard.

Aaron Nattrass, an Aucklander living in Hong Kong, has emerged as a key prosecution witness in the trial of two criminal lawyers charged with trying to prevent a witness in a protection programme from co-operating with the Independent Commission Against Corruption.

It is the latest in a line of public controversies for Mr Nattrass.

He first hit the headlines in New Zealand in 1986 as one of two Otahuhu Borough Council traffic officers who claimed a superior had been falsely endorsing traffic notices.

Within a year, he was back in the news as an immigration consultant helping Hong Kong business people come to New Zealand at $10,000 a go.

Before long he was at odds with the Immigration Service over false job guarantees. After a seven-year legal battle he was acquitted of fraud and forgery charges.

Mr Nattrass brought a private prosecution against the chief migration officer with the New Zealand Commission in Hong Kong, but the case was dismissed.

His latest turn in the headlines comes in a case against lawyers Kevin Egan and Andrew Lam.

China business newspaper the Standard reports that Mr Nattrass is in a witness protection programme. He told the court he was asked by Lam to interfere with a witness.

But in cross-examination Mr Nattrass found his credibility attacked by Lam's counsel Graham Harris.

Mr Harris said evidence of the fantasist life could be found in draft personal column adverts Mr Nattrass had written.

They included claims to be personal lawyer to Philippine President Gloria Macapagal-Arroyo, exotic tales of military service, being wounded in the jungle and airlifted to safety.

He also claimed to have arrested the French secret agents after the bombing of Greenpeace's Rainbow Warrior in Auckland in 1985.

Mr Nattrass told the court that he often joked around and that he would not need personal ads because he had a wife and four girlfriends with whom he had "close intimate relationships".

"I suggest, Mr Nattrass, that you are prone to making up stories," Mr Harris said. "I suggest you have a highly vivid and fertile imagination."

Mr Nattrass, chairman of the Hong Kong Human Rights Foundation, denied "making up any stories". He said he had everything to lose and nothing to benefit from testifying against a former employer.

The Standard reported that despite the challenges, Mr Nattrass maintained his outlandish claims were either true or meant as jokes.

He referred to his first public controversy, telling the court he really had served as a highway policeman in New Zealand.

"What traffic offence arose in the Rainbow Warrior case?" Mr Harris asked.

Mr Nattrass said that was a joke.

The trial continues before district court chief judge Barnabas Fung.