A Kiwi property investor who claims he has been duped out of more than $1million has used a private investigator to freeze Swiss bank accounts of alleged international loan scammer Western Gulf Advisory.

WGA, owned by Indian-born Ahsan Ali Syed, is the same company used by Wellington property developer Terry Serepisos for a yet-to-be-received US$100m (NZ$114m) loan to restructure his Century City group of companies.

McNabb Group Properties – which paid NZ$1.1m in loan fees to WGA for a US$50m loan that never eventuated – has filed criminal complaints against WGA in Switzerland and Bahrain.

The moves follow a series of events that began last August when MGP sought funding for an Auckland hotel and for the Waihi Gold Discovery Tourism Centre, and was approached by WGA's New Zealand middleman, Daniel Hunt. MGP followed due diligence for several months before advancing $1.1m to WGA to cover loan fees.

But alarm bells started to chime in mid-March when the loan did not eventuate on the agreed date and WGA breached the agreement by not returning the fees when requested.

The company hired private investigator Mark van Leewarden, who travelled to Dubai and Switzerland with enough evidence to persuade Swiss banking authorities to freeze WGA accounts. The Bahraini bank accounts of WGA were frozen last month by Australian investors who claimed Mr Ali had scammed them for A$100m.

MGP boss Gary McNabb said WGA had threatened to sue the New Zealand company for US$6m.

"They have no grounds at all in law to sue us. Our contract with them – which is under Swiss jurisdiction – says that if they don't perform, they have to return all our funds to us immediately."

The legal action has so far cost MGP about $100,000 but that is expected to double by the time the final tab comes in.

Mr van Leewarden, who is an investigator, barrister and former police detective, said it became apparent that taking action in Bahrain to recover the money would be fruitless.

"But we knew that funds had been deposited into Switzerland in a Credit Suisse account.

"As a result of that I took steps to freeze the account by making contact with the bank. I also froze a UBS [bank] account in Zurich. I have also filed a criminal complaint with the Swiss attorney-general responsible for white-collar crime."

WGA had caught a lot of people, he said. "They've been clever in the way they operated out of Bahrain ... which has a lot of capital as a country. They targeted people in Australia, New Zealand and Malaysia. They then deposit the funds under another jurisdiction in Switzerland.

"So they are pretty slick. PR companies have been involved and they have touched a lot of people. And they acted like a bank in terms of doing due diligence."

As far as Mr van Leewarden could establish, WGA had never paid out on any promised loans.

Mr Serepisos declined to comment but he has previously admitted to paying undisclosed loan fees to WGA for a US$100m loan which he has been expecting since early this year. He said at the time that WGA would refund the fees if the loan did not eventuate.

Mr Ali, who owns the financially troubled Spanish football club Racing Santander, is also being touted by Mr Serepisos as a potential sponsor of Wellington Phoenix.

WGA middleman Daniel Hunt confirmed he had brokered the deals for both Mr Serepisos and MGP but said that he had not made any money from setting up the deals. He did not believe WGA loans were a scam.

The Dominion Post spoke to a staff member at Mr Ali's WGA office in Bahrain. She said he was unavailable to speak to the newspaper as he was praying but he would call back.

The call never came.