D.C. Police Chief Burtell M. Jefferson joined his predecessor this week in urging Congress to keep the police department at 4,141 officers, saying any cuts would directly reduce public protection against crime.

It does not follow, Jefferson said, that the dramatic reduction of the city's crime rate in recent years justifies having fewer officers on the streets.

Jefferson, two months on the job as the city's first black police chief, chose a friendly forum - the House D.C. Appropriations Subcommittee - for his strong statement condemning the D.C. City Council's recent policy of cutting police manpower by not replacing those who resign or retire.

Last year, prodded by subcommittee chairman William H. Natcher (D-Ky.), then-Chief Maurice J. Cullinane said he felt the attrition policy was wrong, even though he was duty-bound to support it. The subcommittee then voted against cutting the size of the force.

Cullinane's position drew a sharp objection from city council member Marion Barry (D-At Large), a leading supporter of a smaller police force, who is now a mayoral candidate.

Jefferson told a reporter he knew his own remarks this week were contrary to Barry's position, but that they were not aimed at the council member or anyone else in particular.

Currently there is a lapse in the council's police-reduction policy. After voting to cut the police force next year by 171, the council recently reversed itself at Mayor Walter E. Washington's urging and restored $2.6 million to the proposed city budget to keep 4,141 officers on duty.

So Jefferson, in this week's testimony, was not violating any current city policy, but he made it clear that he was attempting to build resistance to any future turnaround. While he may encounter trouble with the council, he will have none with Natcher.

"You hang right in there with this, chief, you've got friends on this side of the table," Natcher told Jefferson.

From 5,100 officers in 1971, Jefferson said the force has dropped to 4,127 now, and under the orginal council plan would have fallen to 3,806. Jefferson has ordered recruitment to bring the force up to the authorized 4,141.

Jefferson said the trend of crime in the city has tended to correlate with the number of officers assigned to police patrol. The more officers, he said, the less crime.

As the police department shrank, Jefferson said, the patrol division was the last unit to be reduced. It stayed above 2,900 officers until last November.

"We have, unfortunately, passed the point where . . . reassignments of personnel (from administrative and support services) can continue, and any future manpower reductions will unavoidably affect the patrol division," Jefferson declared.

"Many of the people who comment on our budget have a tendency to equate 'crime' with (Police) 'workload,'" Jefferson said. "If crime has been reduced, they say, workload has been reduced, and manpower levels should be adjusted accordingly."

That isn't so, Jefferson insisted. One reason crime is down dramatically, the chief said, is the number of police responses to emergency calls - from 881,235 such calls in 1972 to more than 1 million last year, a 16 percent increase in five years.

Also, the chief said, "We're getting tremendous community support and cooperation."

Jefferson cited statistics that reinforce the downward trend of crime, from a total of 89,289 major offenses reported in 1970 to 49,789 in 1977. In that time, Washington went from No. 1 ranking in crime per capita in the country to No. 18 last year.

Preliminary figures for the first three months of this year show a downward trend of 5 percent in reported crime, resuming a trend that was interrupted by a slight upturn in 1977.