Serious crime in the District of Columbia increased 8 percent during the last quarter of 1978 over the same period of 1977, according to recently released police figures.

There were increases in all categories of major crime. The largest increase was in burglaries, which were up 10 percent. Larcenies were up 9 percent, rapes and robberies up 4 percent, homicides up 5 percent, aggravated assaults up 3 percent and auto theft up 2 percent.

Of the seven police districts, only the 3rd District showed a decrease in serious crime, an overall decrease of 7 percent. The district roughly covers the area between L and Harvard Streets NW and Connecticut Avenue and 7th Street NW. The highest increase -- 18 percent -- occurred in the 2nd District, which includes Georgetown, Cleveland Park, the area between the river and Connecticut Avenue to the District line and the business district along K Street downtown.

Police Chief Burtell M. Jefferson, at a ceremony at the 3rd District station, blamed the increases on a number of factors, including unemployment and inflation. Also, Jefferson said, the poor quality of street drugs, especially heroin, forces addicts to steal more in order to purchase greater quantities of drugs to statisfy their habits.

In addition, Jefferson said, citizens have been encouraged to report more crimes because of improved police community relations.

"We have a better working relationship with the community, we have the confidence of the community and I think that is one of the reasons why the people are reporting more of the things that happen to them to us," Jefferson said.

In the other districts the increases for serious crimes were:

lst District, including downtown east of 14th Street and Capitol Hill to the Anacostia River, up 9 percent.

4th District, upper Northwest from Harvard Street to the District line, up 16 percent.

5th District, most of the Northeast section of the city west of the Anacostia River, up 5 percent.

6th District, far Northeast, including the upper part of Anacostia, up 10 percent.

7th District, far Southeast, up 6 percent.