General Services Administration chief Gerald P. Carmen's decision last year to sell a piece of San Francisco property to the city for lease to the Marriott Corp. was made "without sufficient comparative cost data" and on the basis of an appraisal that "may have understated its value," the GSA inspector general reported last week.

The report said no evidence was found "to prove or disprove" charges by some members of Congress that Carmen's decision to override lower level GSA officials' recommendations that the land be swapped for another site on which a federal office building could be built rather than sold was influenced by political considerations.

The inspector general said Carmen should now request an analysis to determine whether it was more in the government's interest to sell the property or seek other land in exchange for it.

In a statement, Carmen said he would follow the report's "relevant recommendations" but asserted that the sale "is in the interest of American taxpayers. . . . Our reasoning for the sale was and is sound."

The city of San Francisco wants to acquire the site, more than an acre in size and valued at $17.4 million in the GSA appraisal, to complete a parcel that could be leased to Marriott for construction of a $100 million hotel.

According to the report, Carmen recalled deciding to sell the property on Oct. 30, but all written documents relating to the decision indicate it was made in mid-November after a meeting between the GSA chief and Marriott representatives. Marriott officials and members of the Marriott family and the firm's political action committee have been major financial contributors to the Republican Party.