NEW YORK ( TheStreet) -- A controversial provision in the current version of the Senate's financial reform bill could lead to dilutive common equity raises at several large banks. The amendment, which was introduced to the Restoring American Financial Stability Act of 2010 by Sen. Susan Collins (R-Maine) and approved on May 15, would exclude trust preferred securities, or TruPS, from bank holding companies' regulatory capital ratios. A vote on the full banking reform bill is still to come. A bank holding company's Tier 1 capital - also known as core capital - is a conservative regulatory capital measure, which excludes non-qualifying preferred stock, unrealized gains on securities, goodwill, and other intangible items including deferred tax assets, but many TruPS are included. Because of their seniority over other share types, TruPS are thought of as "essentially debt" by some analysts and investors. The Federal Deposit Insurance Corp. has long been against including TruPS as part of Tier 1 capital, although the Federal Reserve determined in 1996 that up to 25% of a bank holding company's Tier 1 capital could be comprised of this type of equity. The largest U.S. bank holding companies, including Bank of America ( BAC), JPMorgan Chase ( JPM), Citigroup ( C) and Wells Fargo ( WFC) had relatively small portions of their reported Tier 1 capital in TruPS as of March 31, and the group would see little impact from the amendment. But some holding companies that have higher portions of Tier 1 capital in TruPS look vulnerable and could need to raise additional common equity, depending on how the exclusion ends up being enacted, if it happens at all. In a gently-worded statement, Rochdale Securities analyst Richard Bove said the provision would require that "American banks withdraw from the global financial system because Americans would not be allowed to compete." He went on to say that enacting the amendment as written would "result in the loss by America of the world's core currency and the shrinking of the American economy." Using data supplied by SNL Financial, the following five banks had the highest levels of qualifying trust preferred securities as part of their Tier 1 capital among the largest 50 U.S. bank holding companies as of March 31. The list excludes South Financial Group ( TSFG) because it's since agreed to be acquired by TD Bank Financial Group ( TD). The Tier 1 risk-based capital ratio needs to be at least 6% for a bank to be considered well capitalized under ordinary circumstances. Regulators are still mulling what appropriate capital levels should be for the industry, especially for holding companies that owe the government bailout money received through the Troubled Assets Relief Program, or TARP, or are facing significant loan losses.