Bermuda-based Assured Guaranty Ltd., a financial guarantor and mortgage insurer, said its fourth-quarter results will include a $303 million write-down on credit derivatives.

The unrealised mark-to-market loss equates to $4.39 a share, according to a statement on Business Wire. Assured, which insures bonds and collateralised debt obligations, had previously said its loss from derivatives contracts in October and November was $220 million.

"Our home equity line of credit exposures continue to experience rising delinquencies," said Dominic Frederico, Assured Guaranty's president and chief executive.

However, he added that the remainder of Assured's portfolio, including pooled corporate and US sub-prime residential mortgage-backed securities exposures, was performing in line with expectations. Assured plans to publish full quarterly results on February 11.

Derivatives are financial instruments derived from stocks, bonds, loans, currencies and commodities, or linked to specific events like changes in interest rates.