The D.C. City Council's Finance and Revenue Committee recommended yesterday that District tax assessors reverse their new policy of stressing the value of land over the value of buildings as the basis for real estate taxes.

In a 28-page report, the committee also called upon the city's Finance and Revenue Department to adopt clear and firm guidelines to govern to work of its 44 full-time assessors.

Department officials testified at a committee hearing last March that assessments follow accepted professional standards, but that there are no written rules for assessors to follow.

"Such lack of regulation or guidelines . . . creates an atmosphere where it would be extremely easy for an unscrupulous assessor to flourish," the committee report declared. "There is simply too much power (for the assessors) and too little control over" them.

The report by the committee, which is headed by John A. Wilson (D-Ward 2), has no direct force of law.

One of its strongest recommendations dealt with a new assessment policy that surprised many District taxpayers when they received their assessment notices last January.

Typically, the valuation of land increased sharply while the valuation of dwellings remained relatively stable, or in some instances declined.

In recommending that the new assessment procedure be dropped, the committee said it threatens to upset the relationship between valuations and the size of insurance policies on structures, and also would distort the allowable return on investments granted to landlords under the rent control law.