A businessman at the centre of a $23.5 million fraud inquiry has been living in a sumptuous Sydney apartment, working and playing with glamorous actresses and models.

Gavin Bennett has been accused in court documents of "deceit" over money missing from his DataSouth group of companies.

The Serious Fraud Office is investigating after a corporate whistleblower identified a massive hole in the accounts.

Bennett, sole director and shareholder, says there is a reasonable explanation for the allegedly missing money - but refuses to say what it is.

The $23.5m is likely to be covered by taxpayers. The money was borrowed by one of his companies from South Canterbury Finance Ltd - which was covered by a taxpayer guarantee.

The Herald on Sunday has pieced together the final moments of an 18-year business odyssey by Bennett and the DataSouth companies - Christchurch-based IT businesses that provided a vital lifeline to Canterbury businesses in the wake of the February quake.

The paper has been told of how Bennett set up an Australian arm of the business and began enjoying the high life across the Tasman. He was seen on the town with attractive women 20 years his junior, drinking the finest champagne in some of the city's best bars - and being chauffeur-driven in luxury cars. "He drank Dom Perignon like it was Speights," said one associate.

It is understood the discrepancy in the accounts was uncovered in the weeks after the February earthquake by DataSouth's new chief executive Hayley Bryan, who was hired in October last year.

Documents from a hearing in the High Court at Auckland show it was Bryan who identified problems with the amount of money the company had borrowed from South Canterbury Finance.

The DataSouth group offered its IT clients finance through one of its companies, DataSouth Finance Ltd. That money would be borrowed, in turn, from South Canterbury Finance Ltd - a Timaru-based company that is now in receivership.

It is understood Bryan contacted the Serious Fraud Office after discovering what appeared to be irregularities in the leases. She then set about establishing the amount of money missing.

Court documents state she approached South Canterbury Finance and then asked accounting firm BDO Christchurch to review the books.

A BDO study said many of DataSouth Finance Ltd's customers said they hadn't leased the computed equipment that South Canterbury Finance Ltd had been told they leased.

BDO found that South Canterbury Finance Ltd had lent $25.7m, but DataSouth Finance Ltd had just $2.6m of leases recorded as security.

When Bennett was asked for an explanation, he sent a "substantial list" that he said were not bona fide leases.

On March 31, Bennett put DataSouth Finance Ltd into liquidation. Other companies in the group were also shut down.

The step forced South Canterbury Finance Ltd's receivers to move fast: they won an urgent hearing in the High Court at Auckland to freeze all Bennett's assets, and bar access to his bank accounts.

The judgment from Justice Patricia Courtney revealed Bryan's role as the corporate whistleblower, and stated South Canterbury Finance Ltd had "a strong claim against Mr Bennett for deceit".

Legal documents show South Canterbury Finance Ltd staff were given permission to take over any property owned by DataSouth Business Solutions, also in liquidation - including selling the computer and planning to sell the pot plants.

But in Australia, Bennett is still listed as a director of Australian companies.

He is in business with model Mariesa Crowder, who wanted to run a company to sell lingerie she had designed.

Crowder said she met Bennett when he came to drink at a place where she worked in Sydney. He left her his business card.

"He was going to help me start my company," she said this week.

In March - as Bryan's investigations gathered pace in New Zealand - Bennett helped form Mariesa Mae Pty. He was a director and 10 per cent shareholder and Crowder held the other 90 per cent.

Shortly after starting the company, Bennett told her he could have nothing more to do with it. "We closed the company down about a month ago through an accountant," she said. "That was the last I saw of him."

There was no romantic involvement: "Gavin was a gentleman."

Bennett also spent time with Marlena Davis, listed as a co-director of DataSouth's Australian arm. Davis runs her own business as an image consultant, carrying out wardrobe, style and colour analyses and make-up consultations.

Bennett was photographed at a function with Davis on one arm and his other arm around actress Emily Deyris.

A former associate of Bennett said he was a wild partygoer, who would frequent some of Sydney's best gentlemen's clubs.

The person said he would order bottles of Dom Perignon at the clubs, after being collected from his apartment at The Rocks, which overlooked Sydney Opera House.

Bennett told the Herald on Sunday he had undergone a formal interview with SFO investigators.

"It's subject to a legal situation at the moment. I am co-operating with the receivers, the liquidators and the SFO in this investigation. Everyone knows where I am. I am not running away from anything here."

Asked about the amount of missing money, Bennett said there was disagreement about "the quantification of that".

"I never gained personally from it," he added.

He said there were more than the $2.5m worth of leases that had been identified by BDO.

He also dismissed claims of a wild life. "I think I'm the shy, retiring type."

He said he offered to help set up Crowder's business and provide guidance.

Then, after the Christchurch earthquake, he pulled back because he had too many commitments.

Bennett said he was now working as a consultant in Sydney after the rented apartment he had in Christchurch was destroyed.

As for assets left in New Zealand, he said there would be slim pickings. Even those few at the company would be little use. "I didn't own any pot plants," he said. "They were all rented."