A committee of the D.C. City Council moved yesterday to plug a loophole in the city's recently revamped traffic enforcement program after police officials testified that many motorists and pedestrians are refusing to cooperate with police efforts to issue tickets to them.

Capt. Wayne A. Layfield, commander of the police traffic enforcement branch, said 26.6 percent of all pedestrians and 6.5 percent of all motorists refused to stop or to identify themselves when they were observed violating traffic laws by three special enforcement squads during a four-week period.

Layfield said the statistics were gathered after new traffic regulations went into effect April 13, changing most traffic infractions from criminal violations of law that were enforced in the courts into administrative violations now enforced by civilian adjudicators.

When the new regulations took effect, lawyers for the Police Department reported that officers had lost legal power to compel motorists to follow orders to stop -- except for specific serious violations -- or to display a driver's permit or to compel pedestrians to properly identify themselves.

Mayor Marion Barry promptly asked the council to pass emergency stopgap legislation restoring the lapsed police power and providing criminal penalties for violations. The council did not do so, but its Judiciary Committee held an informal hearing yesterday on Barry's proposed permanent legislation. It then voted 2 to 1, with two members absent, to recommend approval to the full council.

Committee chairman David A. Clarke (D-Ward 1), who reluctantly endorsed the measure, sharply criticized Barry and his predecessor as mayor, Walter E. Washington, for failing to heed warnings by Clarke and others that the shift in traffic regulations would create enforcement problems unless they were carefully drafted.

Layfield, in his statistical testimony, said that in the four-week period there were 4,288 of what the police call "contacts" with motorists, 279 of whom refused to stop or produce their permits. A total of 3,576 citations were issued. Among pedestrians, there were 2,112 contacts, 561 refusals and 1,432 citations.