Unmistakable signals indicate that it's time for the District's urban renewal agency to declare a moratorium on the sale of city-owned commercial property until a new policy can be formulated.

The history of the D.C. Redevelopment Land Agency suggests that it neither understands the dynamics of the marketplace nor its role as a catalyst for economic development. And all the while, developers, financially capable or not, have strung the agency along in a big game of Monopoly.

In increasingly stronger criticism of the RLA board, D.C. Mayor Marion Barry recently noted that it "has not been successful since 1974 in making sure any major development happens in this city."

While it's true that no major city-owned parcel has been developed for commercial use in 10 years, the mayor would have the RLA make hasty decisions that are almost certain to expand the biggest glut of office space in the city's history. Quick discount sales of property to hasten the buildup of more empty office space is hardly a viable alternative for "making sure any major development happens" in the District.

A score of new office buildings downtown stand out as monuments to speculation and miscalculation of economic trends. Development is "happening" but there is little else to ensure that the District will soon gain from new jobs, corporate and payroll taxes and spinoff benefits from services to new buildings.

A recent survey shows that nearly four million square feet of office space remain unoccupied in the five million square feet in new buildings scheduled for completion this year in downtown Washington. At least one million square feet more will be added in 1984, and almost 800,000 square feet of that total remain uncommitted.

The inventory of empty space might have been greater if the RLA had been successful in completing some of the more recent negotiations with would-be developers of city-owned property.

To be sure, the agency dropped the ball in earlier negotiations with developers for the right to develop city-owned property. But chairwoman Nira H. Long states correctly that economic factors such as high interest rates and a glut of office space in recent years have added to the difficulty of arranging commercial land deals.

Given those factors, developers don't want to get in the market and "there is nothing the city can do about that," Long told The Post recently.

But there is something the agency can do to advance development. By maintaining ownership and control over sites it owns, the city can use land as leverage to spur diversified development--not just office buildings. With the necessary infrastructures in proper settings, the District should be able to lease land for a specific purpose at attractive rates.

Montgomery County recently unveiled a project that serves as a model for just such an approach. A year ago, county officials began putting together the pieces for development of a 230-acre tract to be used exclusively for biomedical research.

Companies interested in locating in the campus-like setting of the new Shady Grove Life Science Center may lease sites, with options to purchase. Guidelines and covenants affecting land use, architecture, landscaping and maintenance assure the county that its standards as well as economic objectives will be met.

One might conclude that the Shady Grove venture is a gamble that the District cannot afford. But market analyses by independent economic development consultants indicated a strong demand by biomedical firms for sites in the county.

Similar market analyses may prove beneficial to the District. Related studies may also indicate that the District is in a fairly strong position to insist that developers of city-owned land build more mixed-use projects that include residential space--a natural way of creating the much-talked-about "living downtown."

There may still be opportunities for the District to make more than a token attempt at that type of approach. In recent actions, the RLA has taken a tougher stance with developers by withdrawing development rights to one site and by rejecting a proposal to lower the price at another.

These developments may provide an opportunity for the RLA and the mayor to call the hands of developers and to establish a moratorium leading to a new land-use and disposal policy.