A.M. Best has downgraded Aviva plc’s (U.K.) financial strength rating from A+ to A, following recent financial results that include £2 billion in investment losses. The insurer’s issuer credit rating also fell, from “a” to “a-.”

“A.M. Best is concerned about the level of shareholders’ asset risk associated with AVIVA’s global corporate bond portfolio backing its life and GI businesses (amounting to GBP 26 billion), where the investment mix includes 30% of assets rated BBB or lower,” the ratings agency notes in a statement.

The financial strength rating for Aviva’s subsidiaries, including Aviva International Insurance Ltd., Norwich Union Insurance Ltd. and other European operations, also fell from A+ to A. The issuer credit rating for the subsidiaries was downgraded from “aa-” to “a+.”