Do the Big Four help their clients dodge tax by shifting their money into offshore havens?

You bet, says a report from the British-based Tax Justice Network, a group of a group of accountants and economists concerned about corporations and wealthy individuals avoiding tax by shifting assets overseas.

The report, Closing The Floodgates, says KPMG admits to working in 38 havens but appears to operate in 41, PricewaterhouseCoopers admits to a presence in 25 but appears to be in 38, Ernst&Young admits to being in 38 and Deloittes says its in 29 but is probably in 22.

"The largest firms of accountants in the world operate in locations where opaqueness and not transparency is the hallmark of trade, taxation and regulation,'' the report says.

"Perhaps unsurprisingly all the firms were present in all the major havens. What was not anticipated was the surprising reluctance of three of these firms to acknowledge their operations in the mid range, and especially the minor havens."

Approximately $US11.5 trillion of assets - almost the size of the US GDP - is held in offshore locations and the tax not paid as a result of this trickery could be as much as $US255 billion, says a 2005 Tax Justice Network report.

If the "floodgates" report is anything to go by, it's all made legit by the world's biggest accounting firms.