Key Points:

Dame Margaret Bazley has accused the men at the centre of the police rape trials of using a private investigator in an attempt to discredit her position on the Commission of Inquiry into Police Conduct.

Shortly after the inquiry began in 2004, Dame Margaret became aware that a private investigator had obtained information about the criminal activities of her former husband, whom she divorced nearly 30 years ago.

Her lawyer, John Tizard, says the investigator was acting for suspended Assistant Commissioner Clint Rickards and co-accused Brad Shipton and Bob Schollum in an attempt to discredit the commission.

It is understood that a distressed Dame Margaret took her concerns directly to Prime Minister Helen Clark, believing it was inappropriate to go to the police given that the commission was investigating them.

The information uncovered by the investigator related to Stephen Bazley - whom Dame Margaret divorced in 1978 - and his connections to the "Mr Asia" drug syndicate in the 1970s and 1980s.

Helen Clark retained her faith in Dame Margaret to head the commission, given her record as a top-level public servant in the years since.

The information about Mr Bazley has continued to be circulated, and this week Mr Tizard told the Herald "this material was originally sourced by a private investigator retained on behalf of Messrs Rickard[s], Shipton and Schollum in an attempt to discredit the commission as long ago as 2004".

Dame Margaret could not be contacted this week to answer further questions about the investigator.

Helen Clark said through a spokeswoman that no action needed to be taken because Dame Margaret was "held in the highest regard for her work at the most senior levels of the public service".

"Unfortunately nothing can be done to stop people hiring private investigators to dig into the lives of public figures, as the Prime Minister herself has experienced," the spokeswoman said.

Mr Rickards' lawyer, John Haigh, QC, said he completely denied Dame Margaret's claims and had no idea of her husband's name until told by the Weekend Herald yesterday.

Lawyers for the other two men also denied the allegation.

Mr Rickards was cleared of all criminal charges but remains suspended on full pay, understood to be about $150,000 to $159,000, because of undisclosed employment issues.

Police Commissioner Howard Broad would not comment yesterday, but a spokesman said a private investigator handed over "historic media articles" relating to Mr Bazley in 2004.

Dame Margaret issued her damning report this month, extracting an unprecedented public apology from Mr Broad about historic police behaviour.

Dame Margaret was appointed to head the commission after Louise Nicholas went public in early 2004 with claims she was raped by police officers in Rotorua in the 1980s and the investigation was mishandled.

Dame Margaret became the sole commissioner in 2005 when Justice Bruce Robertson asked to be discharged because of time pressures when the scope of inquiry was altered so it could continue without prejudicing criminal proceedings such as that involving Mr Rickards, Brad Shipton and Bob Schollum.

It is understood that Justice Robertson is unaware of any attempts to discredit him in a similar way, although he presumes it is likely his background was also subject to scrutiny.

Stephen Bazley and Margaret Hope were married in Waihi in November 1965, when he was 29 and she was 27. The marriage was dissolved 12 years later in June 1978. Mr Bazley was named as an associate of infamous "Mr Asia" figure Terry Clark by the Australian Royal Commission of Inquiry into Drug Trafficking report published in 1983.

It said Mr Bazley was a business associate of Clark and known to other notorious New Zealand criminals from that time such as Peter Fulcher and Marty Johnstone.

The report said Mr Bazley had an extensive criminal history dating back to 1956 "and has convictions which led to the New Zealand police describing him as a thief, burglar, car converter, abortionist, sex offender and false pretender".

It said police "suspected Bazley of being involved in cannabis dealing on a large scale from as early as 1974".

Dame Margaret, then a nurse, was matron of Sunnyside Hospital in Christchurch in 1965 and moved on to jobs in Auckland and Hamilton before the marriage was dissolved.

By 1978, she was director of nursing at the Department of Health before shifting into public service management as a State Services Commissioner in 1984.

In the 20 years through to being appointed to the Commission of Inquiry into Police Conduct she held a number of high-powered positions and now, aged 69, is the chairwoman of the Fire Service.

Mr Bazley, who lives in Invercargill, refused to comment when approached this week. It is understood he and Dame Margaret have had little or no contact in the past 30 years and that he has been upset by the attempts over the past three years to link her to his past crimes.

He lived in Australia for a time after the marriage was dissolved and had a media profile in the mid-1980s when an inquiry was set up into corruption in the New South Wales Police after he made claims on an ABC Four Corners programme called "An Informer's Tale".

Now 71, he works for the Southland Beneficiaries and Community Rights Centre.