A new US Internal Revenue Service enforcement unit targeting the very wealthy will help the tax agency decode partnerships, offshore trusts and other complex techniques used to hide income, IRS Commissioner Doug Shulman was quoted by the Wall Street Journal as saying yesterday.

Dubbed the Global High Wealth Industry group, the unit will launch "a small number" of audits of individuals with assets or income in the tens of millions of dollars, Mr Shulman said, according to the publication. An IRS official said the group would begin work on these initial audits in the next month.

The high-wealth group, housed in the IRS's large- and medium-sized business division, marks a sharpening of the IRS approach to auditing the very wealthy. Its creation is a response to the complex web of entities and transactions many high-net-worth individuals use to manage their financial affairs.

"You cannot assess compliance among the nation's wealthiest individuals by looking only at their 1040s [tax returns]," Mr Shulman said. "Our goal is to better understand the entire economic picture of the enterprise controlled by the wealthy individual and to assess the tax compliance of that overall enterprise."

The IRS, along with other US government departments, has been mounting an increasingly fierce campaign against alleged tax evaders, in particular against citizens using offshore accounts. The issue has come under a harsh spotlight this year due to attempts by US authorities to penetrate Swiss bank secrecy.