As Leona Helmsley's famously noted, "Only the little people pay taxes." That could easily apply to U.S. corporations today.

Large American companies have stockpiled $2.1 trillion in untaxed profits in offshore tax havens, with 26 corporations alone accounting for more than half of those profits, according to a new study from the Center for Effective Government and the left-leaning Institute for Policy Studies. In the last 10 years, those offshore profits have surged more than five-fold as corporations seek strategies to reduce their U.S. tax bill.

The massive money stash is causing debate among lawmakers about the best method for convincing those companies, like tech giant Apple (AAPL), to repatriate those profits. One bill from Senators Rand Paul, R-Kentucky, and Barbara Boxer, D-California, for instance, proposes providing a steep incentive: a tax rate for repatriated profits of only 6.5 percent, or far below the full 35 percent rate that would normally be levied. The Paul-Boxer proposal pledges to use the taxes to fund highway repairs.

But providing corporations with a tax holiday isn't the best strategy, especially given that it's failed to work in the past, Scott Klinger, director of revenue and spending policies at the Center for Effective Government, told CBS MoneyWatch.

"It's a just a big game, and a tax holiday incentivizes that game to continue," Klinger said. "We really need a clear signal from Congress and the president that enough is enough. Let's stop the practice first.