Shares of Aflac Inc. (AFL) touched their lowest level since April 2000 Thursday after an analyst said the insurer's exposure to hybrid securities issued by European banks, including Royal Bank of Scotland Group PLC (RBS), is a "rapidly escalating concern."

Aflac shares fell as much as 39% in morning trading after Morgan Stanley analyst Nigel Dally told the firm's clients to avoid Aflac's stock owing to its $7.9 billion of exposure to securities that have been sharply marked down after European financial firms announced large losses this week. In early afternoon trading, shares were still down 32.8%, to $24.38.

"If even a small portion of these losses are realized, the hit to Aflac's capital ratios could be substantial, and their overall capital adequacy could be significantly less than most investors believe," he said.

Aflac disagreed. Laura Kane, an Aflac spokeswoman said Thursday the company is "comfortable with our current capital position and are constantly monitoring our investment portfolio," She said Aflac will offer more "specific details" along with its earnings release Feb. 2.

The growing trend toward government takeovers of banks, called nationalization, calls into question the eventual status of the so-called hybrid securities, bank-issued notes that have elements of both equity and debt.

If the hybrid securities are classified as a form of equity after a government takeover, "it would be akin to the creation of a new toxic asset class," said Raymond James analyst Steven D. Schwartz in an interview.

Although debt holders were largely "taken care of" after the U.S. government stepped in last year to bail out U.S. mortgage companies Freddie Mac (FRE) and Fannie Mae (FNM), equity holders were not, Schwartz said. He said investors are worried that hybrid securities holders in government-owned E.U. banks could face the same fate.

The issue of whether these securities should be considered equity or debt has already come up, said Kriss Cloninger, Aflac's chief financial officer, in a December presentation at a Goldman Sachs conference.

"And our hybrid securities, the bank capital notes basically, all have an economic maturity date," Cloninger said. "And we had always hung our hat on the fact that these should be accounted for as debt instruments because they have an effective economic maturity date that was in essence the same as the stated maturity date."

In October, the Center on Audit Quality advised that unless a security had a specific maturity date, it should be treated as equity for determining when impairments on the value should be recognized as being other than temporary in accounting statements, Cloninger said. The Financial Accounting Standards Board is currently considering the issue and has not made a decision.

Although the FASB's determination will affect accounting rules, the debate underscores the unsettled definition of the securities, which make up a substantial portion of Aflac's investments.

"Regarding the classification of hybrids, with the concurrence of our auditors, we've carried them as debt instruments for 15 years, and we believe with good reason," Cloninger said in October, during the company's third-quarter earnings conference call. "In fact, had our auditors not agreed that they were debt instruments for accounting purposes, we probably never would have bought them."

Dally said the value of securities issued by Royal Bank of Scotland, which said Monday its losses last year could be the largest corporate losses in the history of the U.K., dropped as low as 15 cents on the dollar this week, while similar securities issued by other European banks have declined 30% or more to well below 50 cents on the dollar in many cases.

About 80% of Aflac's $7.9 billion hybrid securities come from European financial institutions including RBS, Dally said.

He estimated if Aflac was to take a hit from its exposure to these securities of more than 15%, its capital ratio would decline to a level where its credit ratings would be at risk and the company might need to consider taking steps to raise more capital.

Dally said Aflac's rationale for holding the securities was based on the idea that the European banks would be viewed by the governments as too large to fail.

"Faced with a distress scenario, Aflac believed the respective governments would step in to provide support," he said.

So far, the U.K. has backed that idea up, injecting GBP37 billion ($51.3 billion) into RBS, HBOS PLC and Lloyds TSB Group PLC.

But after RBS said Monday its loss during 2008 would be between GBP22 billion and GBP28 billion, it became clear that the U.K. government would have to commit more to prop up its failing banks, and investors feared it would have to go so far as to nationalize them.

Dally said Aflac's bet that the U.K. will backstop RBS and other banks is risky, because if it and other banks are nationalized outright, all classes of stock, including the preferred shares Aflac holds, could be wiped out.

Just over $5 billion of the company's market value has been wiped away so far Thursday.

-By Ed Welsch, Dow Jones Newswires; 201-938-5244; edward.welsch@dowjones.com and Lavonne Kuykendall, Dow Jones Newswires; (312) 750 4141; lavonne.kuykendall@dowjones.com

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