District Mayor Marion Barry yesterday warned Washington's real estate industry that they could continue to be "at loggerheads for a while, until there is a dramatic breakthrough in the housing supply."

The Washington Board of Realtos and thre Mortgage Bankers Association of Metropolitan Washington, which held their annual convention here last week, asked the mayor for "a sign, a light at the end of the tunnel" that rent control would be phased out. Facing ever-rising costs, D.C. landlords who are unable to increase rents have been selling out in increasing numbers to developers converting rental units to condominiums.

Barry said that a quick end to rent control was "out of the question politically." As for lifting controls on so-called luxury buildings, he expressed concern about investors not inlcuded in the luxury category. "What happens to those left with mandatory rent controls?" he asked.

Calling the condo conversion situation "traumatic," the mayor said he was nevertheless opposed to an across the board moratorium on conversions. Robert L. Moore, director of Housing and Community Development in the District, criticized some apartment building owners for abusing conversion certificates. They are "a new kind of food stamp," he said. "Some people have held conversion certificates since 1976 but have no intention of converting. All they are doing is trying to drive the price of housing up before selling out to a developer."

Another realtor asked the D.C. government to furnish more statistics on the vacancy rate, explaining that housing decisions are now being made on an emergency basis without data.

Despite these frank exchanges, the mood was cordial. Barry said thre District will have a one-stop registration center for permits by the start of next year. D.C. Council Chairman Arrington Dixon asked for the realtors' cooperation in developing a comprehensive plan for the city.

Dorothy J. Kennison, newly appointed D.C. rent administrator, said she would form an advisory committee soon composed in part of realtors and landlords was well as consumers. She also asked the realtors and mortgage bankers to consider innovations such as inviting tenants to invest in apartment buildings as limited partners and long-term lease arrangements whereby tenants take over the management of buildings.