A man accused by American authorities of involvement in a $550 million fraud once helped host an investment seminar in Fiji attended by Act MP Rodney Hide.

The Herald has learned that Grant Thomas Cardno was a key figure at the 1999 seminar, run by a company called Investors International.

Mr Hide has already been criticised by his parliamentary colleagues for attending the seminar, after some of its organisers later went to jail for their part in a Ponzi scam alleged to have fleeced more than 150 New Zealanders of about $10 million.

The scam claimed to be a way of avoiding tax by diverting money through the tax haven of Panama.

It was later revealed that most of the cash was used by its promoters to buy property, motorbikes and travel.

In 2002, a man who lost money after investing in the scheme claimed he was influenced by Mr Hide's attendance at the Fiji event.

In an affidavit read out in Parliament, the man claimed he and his wife discussed Mr Hide's speech at the seminar "and thought that with a member of Parliament and, as he said, a member of the Government, that his support of this conference helped satisfy us that the conference and the opportunities being provided to us would be fair and firm".

Mr Hide has denied any responsibility, saying he did nothing more than give a speech about tax at the event.

He said at the time he had not endorsed anything suggested by Investors International, and the Securities Commission had assured him it did not have any concerns about his role.

He said yesterday he had no further comment, but he was the sort of person who would speak to any group if asked.

In 2001, one of the men behind Investors International was arrested in the United States and eventually went to jail. Four New Zealanders were also given jail terms after a trial in Auckland in 2004.

A year later, Mr Cardno was named by the US Securities and Exchange Commission as being involved in a similar high-yield investment scheme involving up to US$390 million (nearly $550 million at today's exchange rates) from more than 1400 American investors.

Mr Cardno is alleged to have offered similar schemes in New Zealand and according to New Zealand investors, owes them millions of dollars.

The Serious Fraud Office has said it will look into investors' complaints.