4 Corners expose the secrets of the super rich and the shadowy world of secret international finance and tax avoidance.

HUNDREDS of Australians — ranging from convicted fraudsters to one of the nation’s biggest companies — have been caught up in a massive leak involving the tax affairs of the world’s rich and famous.

The Australian Taxation Office said yesterday it was investigating more than 800 Australians named as clients of secretive Panama-based law firm Mossack Fonseca, the target of history’s largest leak of financial documents.

The firm sets up offshore companies, often in tax havens that can be used to help wealthy people and companies dodge tax.

Among those implicated in the leak are the King of Saudi Arabia, Pakistani Prime Minister Nawaz Sharif, Syrian President Bashar al-Assad, the godfather of Russian President Vladimir Putin’s daughter, football star Lionel Messi, actor Jackie Chan, and the father of British Prime Minister David Cameron.

ABC TV’s Four Corners program said Australian-related names mentioned in the files included mining giant BHP Billiton, government contractor Wilson Security, Gold Coast based company director Ian Taylor, and Hong Kong’s richest man Li Ka-Shing, whose company owns a big slice of Australia’s electricity market.

There is no suggestion of any improper or illegal conduct on the part of Mr Taylor or his family.

“What we’re looking at is easily the biggest leak in history in terms of size,” International Centre for Investigative Journalism director Gerard Ryle told the program. “We’re looking at more than 11 million documents,” he said.

“Where people want secrecy, they go to Mossack Fonseca first.”

BHP Billiton strenuously denied on the program that its British Virgin Islands finance companies were used to avoid tax. “BHP Billiton does not engage in aggressive tax planning,” it said.

ATO deputy commissioner Michael Cranston said it had identified more than 800 individual taxpayers named in the law firm’s data, including wealthy individuals who had not previously come forward.

“We are already taking action on those cases,” he said.

“Through data analysis we have been able to identify patterns such as clusters of individual taxpayers and advisers for further investigation.

“The message is clear — taxpayers can’t rely on these secret arrangements being kept secret and we will act on any information that is provided to us.”

Tax lawyer Mark Leibler, senior partner of commercial law firm Arnold Bloch Leibler, said technology was making it easier for sensitive financial information to be stolen.

“It would take a skyscraper to store all those documents, but they’re sitting in a computer somewhere,” he said.

“It’s not surprising — there will be more of this.”

Mr Leibler said clients of Mossack Fonseca would include some serious criminals, people who used tax havens to avoid their tax responsibilities, and those who used offshore companies in a “completely innocent and above-board” way.

“You don’t want to jump to conclusions,” he said.

Those with something to hide should contact the ATO, rather than wait to be investigated, if they wanted to reduce potential penalties, Mr Leibler said. “Coming forward is always the best policy.”

Labor senator Sam Dastyari said avoiding tax was not a victimless act.

“Every dollar that’s minimised is a dollar that’s not going to a school, it’s not going to a hospital, it’s not going to a service that we require and need,” he said.