AM Best Co. has affirmed the financial strength ratings of B++ (Good) and downgraded the issuer credit ratings (ICR) to "bbb" from "bbb+" of The Steamship Mutual Underwriting Association (Bermuda) Limited (Steamship Bermuda) (Bermuda) and The Steamship Mutual Underwriting Association Limited (Steamship London) (United Kingdom). The outlook for these ratings has been revised to negative from stable.

Concurrently, A.M. Best has withdrawn the ratings at the companies' request and assigned an NR-4 to the financial strength ratings and an "nr" to the ICRs.

The ICR of Steamship Bermuda has been downgraded due to weakening in risk-adjusted capitalisation resulting from substantial investment losses.

Despite some early signs of improvement in Steamship Bermuda's underwriting performance, Best believes the marine protection and indemnity market remains competitive. Additionally, Steamship Bermuda is exposed to continuing uncertainty in investment markets.