london (Bloomberg) — The outlook for European insurers is "negative" because of investment losses and weaker earnings, Moody's Investors Service said.

"Earnings prospects for the first quarter, and indeed for the rest of the year, already appear constrained," the ratings firm said in a report on Friday. Moody's has already carried out "negative rating actions" on some European insurers because of concerns about investment risk, earnings and financial flexibility, it added.

Financial-services companies are battling an economic slowdown and the worst financial crisis since the Great Depression. Many insurers are struggling after tumbling markets reduced the value of their investments.

European insurers have reported $28.8 billion in write-downs and credit losses since the start of the credit crisis, compared to $12.3 billion in capital raised, according to Bloomberg calculations. Almost 6,000 jobs have been cut during the period.