Rich Kiwis have been stung with extra tax bills as the result of a huge file leak revealing the global super wealthy hid millions of dollars from tax authorities with the help of HSBC's Swiss private bank.

Inland Revenue investigated New Zealand links to the leaked files and revised people's tax bills upward as a result.

The tax department could not confirm whether anyone would be prosecuted, saying investigations were still ongoing.

While tax avoidance is legal, deliberately hiding money to evade tax is not, and a tranche of leaked files appear to show HSBC's overseas staff actively helping some clients dodge detection.

The secret files list more than 100,000 clients with links to Swiss bank accounts, including a highly respected former New Zealand judge. The leaked bank documents, showing HSBC using its Swiss private banking subsidiary to hide millions, have accounts owned by shell companies registered to Niue, a single island of 1600 people, legally part of the Realm of New Zealand, 2400 kilometres northeast of Auckland.

Niue's currency is the New Zealand dollar.The International Consortium of Investigative Journalists (ICIJ), which obtained the files, has highlighted 63 prominent people globally who were linked to Swiss bank accounts, while stressing they may not have broken the law.

People caught up in the splash include the late New Zealand judge and top barrister Sir Ian McKay, who died a year ago aged 84, the actor Christian Slater, model Elle MacPherson and a slew of bankers, politicians and sportspeople.

The documents do not reveal Sir Ian's exact links to accounts holding a total of US$31,118 (NZ$41,851), says ICIJ.

The leaks also drew links between HSBC and less savoury characters.

"HSBC profited from doing business with arms dealers who channelled mortar bombs to child soldiers in Africa, bag men for Third World dictators, traffickers in blood diamonds and other international outlaws," ICIJ reported.

The files secreted away by a former HSBC employer were passed to tax authorities in different countries, including France in 2008 and Britain in 2010.

In New Zealand the Inland Revenue confirmed it investigated the information "as part of our regular offshore programme of work," however it could not go into detail about any individuals.

HSBC has acknowledged wrongdoing, claiming deep reforms were made after the leak period and saying the "old business model" of Swiss private banking was no longer acceptable.

In a statement Franco Morra, chief executive of the HSBC Private Bank in Switzerland, said much had changed since the period in 2006/2007 to which many of the financial information relates.

"HSBC's Swiss Private Bank began a radical transformation in 2008 to prevent its services from being used to evade taxes or launder money. New senior management have comprehensively overhauled the business," he said.

Still, a panel of British lawmakers, the Public Accounts Committee, plans to open an urgent inquiry after HSBC admitted compliance failings by its Swiss subsidiary.

HSBC in New Zealand, which does not have a private banking arm, did not want to comment on any implications for its local reputation.

ICIJ says McKay, a former member of the Privy Council who was knighted in 1998, was linked to two client accounts at HSBC. One of them held no money in 2006/2007 and the other listed five bank accounts that together held US$31,118 at that time.

However, the leaked files do not specify the exact role that McKay had in relation to the accounts, or whether the accounts were held on trust for other persons.

Inland Revenue's International Revenue Strategy Manager John Nash said the scale of overseas activity in New Zealand was "relatively low" compared to Australia or Europe.

"On average Inland Revenue assesses around 200 tax payers a year and collects around $10 million of additional tax from our offshore compliance activities."

"We collect financial information from multiple domestic sources, in particular financial institutions and any promoters of financial products, and internationally through our tax treaty network," he said.

"In recent years Inland Revenue has been getting more and better information than ever before from overseas and we have very close working relationships with major tax treaty partners."

Asked if Inland Revenue had investigated New Zealanders based on the leaked files, Nash said he could not disclose any information about specific tax payers.

But Inland Revenue confirmed that it investigated the information as part of its "regular offshore programme of work".

Asked if it resulted in extra payments or prosecutions it said it had assessed additional tax, however investigations were ongoing.

HSBC faces criminal investigations in the United States, France, Belgium and Argentina but not its home country of Britain, according to the BBC.

The files showing accounts holding more than US$100 billion in total are based on data secreted by Hervé Falciani, a former HSBC employee.

Thousands of pages of data were obtained by the French newspaper Le Monde and passed to the International Consortium of Investigative Journalists, the Guardian newspaper, Panorama and other media outlets in a joint investigation.

British HM Revenue and Customs has identified 1,100 people from the list of 7,000 British clients who had not paid their taxes. But almost five years later, the BBC reports that only one tax evader has been prosecuted.

HMRC said £135m (NZ$276.6m) in tax, interest and penalties have now been paid by those who hid their assets in Switzerland.