WASHINGTON - Apple has avoided paying tens of billions of dollars in U.S. taxes by creating a complex web of subsidiary companies, particularly three in Ireland, a new Senate investigation has found.

The company is not accused of breaking the law, but senators said Apple seemed to use as much creativity in developing its tax practices as in developing the technology that has turned it into America's most profitable technology business.

"It technically may be in compliance with the law, but it violates the spirit of the law," said Sen. Carl Levin, D-Mich., chairman of the Permanent Subcommittee on Investigations. "It's like saying you haven't shifted the golden eggs offshore after you transferred the golden goose offshore."

The Senate committee, which conducted similar investigations last fall of Microsoft and Hewlett Packard, accused Apple of operating subsidiaries in Ireland that were exempt from filing taxes. One company has paid no income taxes to any nation in five years, according to the Senate investigation, even though it was effectively run by officials at Apple headquarters in California.

Apple officials, including chief executive Tim Cook, are scheduled to testify Tuesday before the Senate committee. They will respond to the findings contained in the 40-page investigation, aides said, and defend the company over the last year for being the "largest corporate income tax payer in the U.S., having paid nearly $6 billion in taxes."

That explanation was unacceptable to Sen. John McCain of Arizona, the ranking Republican on the committee, who delivered a blistering assessment of Apple's practices.

"Apple claims to be the largest U.S. corporate taxpayer, but by sheer size and scale, it is also among America's largest tax avoiders," McCain told reporters at the Capitol late today. "A company that found remarkable success by harnessing American ingenuity and the opportunities afforded by the U.S. economy should not be shifting its profits overseas to avoid the payment of U.S. tax, purposefully depriving the American people of revenue."

The Senate committee found that Apple kept at least $74 billion from the Internal Revenue Service from 2009 to 2012. The accounting practices were so unusual, investigators said, that one likened it to "playing Whac-A-Mole," with a series of loopholes so complicated that even seasoned tax experts struggled to sort through it. After investigating Apple for 18 months, Senate investigators said one of the Ireland subsidiaries was only discovered Sunday evening.

One of the Apple subsidiaries in Ireland reported $30 billion in net income during that period, but filed no corporate tax return and paid no income taxes to any government. The company also did not pay federal taxes on $44 billion from intellectual property rights over the last four years.

"Apple wasn't satisfied with shifting its profits to a low-tax offshore haven," Levin said. "Apple then successfully sought the Holy Grail of tax avoidance."

The committee is releasing its findings to build support for a major overhaul of the nation's tax code. It is the first time Cook and the Apple executives have appeared before a Senate committee. The company sought to get ahead of the report by releasing its testimony late today, vigorously defending its business practices.

"Apple does not use tax gimmicks," Cook will say, according to a copy of his testimony released by his company. "Apple does not move its intellectual property into offshore tax havens and use it to sell products back into the U.S. in order to avoid U.S. tax."

He is also planning to propose a "dramatic simplification" of American corporate tax laws that are intended to encourage businesses to return foreign earnings to the United States. While Apple will be singled out at the hearing on Tuesday, it is hardly the only company that keeps its profits off-shore.

A JPMorgan report found that more than 1,000 U.S. companies have an estimated $1.7 trillion in earnings overseas. Apple has reported having $145 billion in cash, but analysts estimate the company only has $45 billion available in the United States.