The IRS, Teasury Department and Justice Departments have moved on Ernst & Young and other leading firms it believes are the big names behind the tax shelter business. Is this just the beginning?

The government is pressing a broad assault on the flourishing tax shelter business with an array of high-profile summonses and civil suits aimed at stopping cheats who are getting away without paying many billions of dollars in taxes.

These actions come after a decade in which enforcement of the tax laws grew so lax that the tax-shelter industry flourished and tax crimes, like opening secret offshore bank accounts, openly advertised.

In its attack on tax shelters the government is using a strategy known as general deterrence.

Instead of trying to catch every offender, a policy known as specific deterrence that is applied against street criminals like drug dealers, the government is only going after a few big name firms and individuals. By doing so in highly public ways the government hopes to persuade others that it is in their best interest to reform their tax shelter business, which is just what Ernst & Young has done.

Mark W. Everson, the new I.R.S. commissioner said last month that “the I.R.S. will enforce the law across all sectors, but with particular vigor in the corporate arena and for high-income individuals who enter into abusive shelters to game the system.”

After a decade in which the number of auditors, tax collectors and special agents shrank by more than a fourth even as the tax system grew larger and more complex, the capacity of the I.R.S. to press the battle is severely limited, a variety of tax law experts said. All but one of those interviewed last week warned that the I.R.S. will be always outnumbered, always outgunned, unless Congress spends significantly more on tax law enforcement.

Elliott H. Kajan, a tax defense lawyer in Beverly Hills, Calif., said that unless taxpayers incur penalties, which can range as high as 75 percent of the taxes evaded, there is little reason to reject a tax shelter deal.

“The worst that can happen is no harm, no foul,” Mr. Kajan said. “You just pay the taxes and the interest,” which is often a better deal than paying the taxes when they were originally due.