NEW YORK (Bloomberg) - Bermuda-based Assured Guaranty Ltd., the bond insurer backed by billionaire Wilbur Ross, said its pretax loss expenses rose five-fold to $114.8 million last quarter, mainly because of rising costs associated with souring home-loan bonds.

Loss and loss adjustment expenses rose to $90 million from $17.6 million a year earlier, while incurred losses on credit derivatives climbed to $24.8 million, from $500,000, Assured said in a statement distributed by Business Wire.

Rising mortgage-bond losses amid the US housing slump have hobbled the bond-insurance industry. Assured and Dexia SA's Financial Security Assurance Inc. - which Assured agreed to buy two months ago - in November became the last of the companies with top insurance ratings to lose the grades from at least one of the largest ratings firms.

The so-called present value of Assured's direct gross written premiums, a measure of new business, declined 22 percent in the fourth quarter on a plunge in insurance on structured- finance securities and in markets outside the US, Assured said. US public finance business under the measure climbed 124 percent.

Yesterday, the company announced a quarterly dividend patyment of 4.5 cents per share.

Assured fell 46 cents (5.8 percent) to $7.44 in New York Stock Exchange composite trading. The shares are down 70 percent over the past year.