Sen. Patrick J. Leahy (D-Vt.), chairman of the Senate District Appropriations Subcommittee, has asked the General Accounting Office to find out what happened to $2.7 million that Congress appropriated last year to improve conditions at Forest Haven, the city's beleaguered institution for mentally retarded.

The request Wednesday for an audit of the funds was prompted by testimony presented the subcommittee two weeks ago that indicated sub-standard conditions still exist at the facility in Laurel. Congress had provided funds to hire 188 more employes than had been requested by the District government.

Sen. Dennis DeConcini (D-Ariz.) said he had asked Leahy to call for the audit after presiding at the hearing.

DeConcini said he was "pretty well shocked" at descriptions of conditions at the facility, which is home to more than 1,000 persons.

Leahy said his committee is willing to provide additional money for Forest Haven but he first wants assurances that it is needed and will be used well.

Frank Medico of the GAO audit division said Leahy's request probably would be turned over to GAO's human resources division, and that the results should be ready by the Sept.1 deadline sought by Leahy.