Standard & Poor’s Ratings Services has increased its scrutiny of mortgage insurer Financial Guaranty Insurance Company, placing its “double-B” financial strength rating on CreditWatch with negative implications.

The FGIC rating previously had a negative outlook. S&P said Friday that it has placed all other FGIC ratings, as well as those of parent company FGIC Corp., on CreditWatch with negative implications.

Back in March S&P put the FGIC “A” rating and the FGIC Corp. holding company “triple-B” rating on CreditWatch with negative implications. S&P said then it did not like FGIC’s announced plan to split into two firms, with one keeping its less palatable risks.

In its latest statement on the company, S&P said the restructuring scenarios under consideration raise a concern that the surviving corporate entity, FGIC, and the remaining policyholders may be disadvantaged compared with other classes of policyholders–in particular, municipal policyholders.

The rating firm said its latest CreditWatch addresses a concern “regarding the magnitude of the firm’s projected losses from RMBS [residential mortgage backed securities] and CDO [collateralized debt obligations] when compared with its claims-paying resources.

In the next several weeks S&P said it expects to “know more about the company’s direction and will take rating action as necessary as information becomes available.”

Last week the New York-based rating service also took action on two other mortgage insurers, lowering the ratings for Ambac Assurance Corp. and MBIA Inc. In addition, both companies were placed on rating watch with negative implications.

The holding companies of Ambac and MBIA were also lowered one notch from “double-A” and “double-A-minus” to “A” and “A-minus,” respectively.

S&P said the actions reflect its belief that the companies face “diminished public finance and structured finance new business flow and declining financial flexibility.”

The rating agency also pointed to the deterioration of the subprime mortgage market crisis, where both companies insured a significant amount of collateralized debt obligations.

S&P said there will be increased pressure on each company’s ability to pay obligations. The revised ratings support the companies’ claims-paying ability and liquidity levels, S&P said.