Before Gov. Kempthorne put his signature on the bill, several insurers and their associations had urged a veto of Senate Bill 1408.

Michael Harrold, Northwest regional manager of the Des Plaines, Ill.-based National Association of Independent Insurers, expressed disappointment at the governor's action. According to Mr. Harrold, the legislation will be harmful to consumers because of "ambiguity in the new law."

Insurers battling to keep credit scoring as a permitted procedure have lost the fight in the Washington legislature as well, while in California and Maryland such measures have been passed by one chamber. In Alaska, Arizona and Missouri, measures have been released from one committee and a floor vote is pending.

Mr. Harrold said that in Idaho he objected to the law's provision prohibiting insurers from taking certain actions based "primarily" on the use of credit history.

"Since insurers are unsure how to comply with the 'primarily' language, which may also lead to litigation, they may decide not to use insurance scores at all," Mr. Harrold said.

"That would be unfortunate for most consumers," he continued, "because they then will not receive the lower insurance premiums to which their favorable scores would entitle them. Most consumers will end up paying more for their insurance to subsidize individuals who are higher risks."