(Bloomberg) -- Greenlight Capital Re Ltd., the reinsurer thatcounts on hedge fund manager David Einhorn to oversee itsinvestment portfolio, plunged the most since 2010 after posting itsthird-straight unprofitable quarter on stock market losses and poorunderwriting.

Greenlight Re fell $2.07, or 8.4 percent, to $22.67 at 10:45a.m. in New York trading. That extended its slump for the year to31 percent.

The third-quarter loss widened to $219.7 million from $51.8million a year earlier, the Cayman Islands-based reinsurer said ina statement Friday after markets closed. Ratings firm A.M. Bestlowered its outlook on the company to negative from stable, a movethat could make it harder to win new business, according toGreenlight Re.

The reinsurer is pressured by “leverage resulting from aninvestment portfolio that is primarily composed of publicly tradedequity securities,” the ratings firm said in a statement. Also,Einhorn’s company is facing competition from other reinsurers withsimilar investing approaches, A.M. Best said.

Greenlight Re lost $191.3 million on its investment portfolio,fueled by declines in Consol Energy Inc., SunEdison Inc. and MicronTechnology Inc. A year earlier, the investment loss was $54million.

‘Third-Party expert’

Greenlight Re said it was working with a “third-party expert” asthe company reviews insurance liabilities. Insurance underwritinggenerated a loss of $27.6 million, compared with income of $4million in last year’s third quarter.

“There is the potential for new business generation to bemarginally impacted” by A.M. Best’s move, the reinsurer said Fridayin a regulatory filing.“While competitive market conditions havemade finding and successfully underwriting new business that meetsour targeted return hurdles challenging, we believe that we have astrong pipeline of attractive opportunities.”

Einhorn’s reinsurer went public in 2007, selling shares at $19 apiece. Reinsurance ventures in offshore locations can give hedgefund managers tax advantages and the access to more capital forinvesting.

Dan Loeb’s Third Point Reinsurance Ltd. had an initial publicoffering six years later. Third Point Re slipped 11 cents to$13.89. The company has dropped 4.1 percent this year after a 22percent slump in 2014.

--With assistance from Katherine Chiglinsky in New York.