The House District Committee will conduct hearings into reports that Metrobus service is more reliable in the suburbs than in the city, D.C. Del. Walter E. Fauntroy said yesterday.

"This disparate treatment can no longer be tolerated, particularly when the Metro system was established as a regional system with the goal of providing equal service to all jurisdictions," Fauntroy said in a prepared statement.

Fauntroy, the District's nonvoting representative in Congress, said he was referring to a survey conducted by The Washington Post with extensive help from Metro. The results, published Wednesday, showed that bus trips in the District tended to be cancelled or cut short more often than trips in the suburbs.

Buses primarily serving D.C. residents lost 2.2 percent of their trips in the seven-month survey period; service was most reliable in Virginia, with only 0.5 percent of trips lost. Buses mainly serving Maryland riders lost 1.3 percent of their trips.

"We intend to get to the bottom of this problem and at minimum to get commitment for improvement on the record within a mutually acceptable time frame," Fauntroy said.

Metro and city transportation officials, as well as route and maintenance supervisors and garage workers, will be called to testify, he said. The hearings may also explore safety issues raised by the derailment Jan. 13 of an Orange Line train that killed three people.

Metro General Manager Richard S. Page said yesterday that Metro inherited the service discrepancies when it took over four private bus companies in 1973 and had worked to correct them.

Metro will cooperate with the hearings, Page said, noting, "I think it's important for the Congress to understand the conditons under which Metrobus operates and to understand the improvements that have been made. And maybe we can learn about other improvements that we ought to be making."

District Committee Chairman Ronald V. Dellums (D-Calif.), the one to call the hearings, could not be reached for comment. But an aide said that Dellums' normal policy is to defer to Fauntroy in matters that relate directly to the city.