Stephen Searby, a London-based credit analyst for S&P, said the downgrades mostly reflect S&P's reevaluation of reinsurance industry risk and Swiss Re's position within that industry, following a "relative underperformance" in its non-life underwriting profitability.

Mr. Searby added that these ratings downgrades also take into account Swiss Re's slower-than-expected recovery in earnings. This laggard recovery, he said, could hurt the company's ability to fully replenish capital during the current hard phase of the cycle.

Mr. Searby also pointed to a number of positive factors at Swiss Re, including its "very strong business position, superior management team and very strong financial flexibility."

Further, he said S&P expects the combined ratios of the property-casualty to improve to 100 percent and the ratio for the company's financial services business groups to reach 95 percent for the current year.

Separately, Moody's Investors Service announced today it has assigned a "Ba3" rating to a new catastrophe bond offering designed to help Swiss Re.

This new $23.6 million CAT bond offering is from Oak Capital Ltd., a special purpose, Cayman Islands-based exempted company that will benefit Swiss Re. Moody's explained that investors in these notes would provide four years of reinsurance coverage to Swiss Re, limited to $23.6 million against potential cumulative losses from certain windstorms in Europe.

The New York-based ratings firm said its review has provided "sufficient comfort" that the resulting ratings fully capture the risk to investors in these securities.