WASHINGTON — New York's attorney general sued one of the country's largest mortgage appraisers yesterday for inflating house values, saying it would be the first in a series of cases to attack pervasive conflicts of interest that contributed to the housing crisis.

Andrew Cuomo filed civil charges against a subsidiary of First American Corp. for buckling under pressure from mortgage lender Washington Mutual, its top client, at the expense of as many as 262,000 consumers who may have purchased houses at artificially high prices since last year.

WaMu, as it is known, was not included in the lawsuit because of questions about state authority over federally chartered lending institutions.

Cuomo's investigation is likely to have national impact because of the prominence of his targets and his bully pulpit in the country's financial capital. Cuomo's conflict-of-interest settlement with Sallie Mae earlier this year was seen as a watershed in the investigation of the student loan industry. Action against First American, which provides title insurance, closing services, credit reports and home warranties in many states, comes after a nine-month investigation of fraudulent practices that injure both home buyers and investors.

"This is certainly not isolated to New York, and it's certainly not limited to this particular case," said Terry Dunkin, president of the Appraisal Institute, a professional organization that is working with Rep. Paul Kanjorski, D-Pa., on legislation that would increase penalties for appraisers who fail to maintain their independence and lenders who lean on them.

"It's an issue that competent, scrupulous appraisers have been dealing with for several years now," Dunkin said.

Appraisals are the bedrock of the housing industry, with lenders, brokers, real estate agents and home buyers all relying on their accuracy. With the credit and housing crunch likely to result in more than 2 million foreclosures, experts say that exaggerated home prices have contributed to the crisis.