The D.C. City Council voted yesterday to prohibit temporarily the further conversion of apartment buildings into apartment hotels.

By a unanimous voice vote, the council approved emergency legislation that would be effective for 90 days if signed into law by Mayor Marion Barry.

The measure was approved on the eve of a hearing today on proposals by the owners of two apartment houses, the Winthrop House on Massachusetts Avenue and Sherry Towers in Foggy Bottom, to convert the long-term residential facilities with about 400 units into accommodations for transients.

The proposals, to be heard by the D.C. Board of Zoning Adjustment, have been protested by tenants who fear displacement.

The emergency legislation was introduced by John A. Wilson (D-Ward 2), who represents the area where both apartments are located and co-sponsored by David A. Clarke (D-Ward 1).

An aide to Wilson said about 4,000 apartment units throughout the city already have been converted into transient facilities, increasing pressure on rental properties caused by large-scale conversion of buildings into condominiums.

The city already has a moratorium on the conversion of apartments into condos. Permanent condo legislation has been enacted by the council and is awaiting the mayor's signature.

Under the new emergency law, the only apartments that could be rent to transients would be those in which 60 percent of all units already are subject to the city sales tax imposed on hotel occupancy.