Consumer prices in metropolitan Washington rose 1.1 percent during December and January, mainly because of higher housing, grocery store and medical services costs, the government reported yesterday.

The two-month increase in area prices exceeded slightly the 1 percent avearge rise for all U.S. cities. On an annual basis, Washington area prices last month were up 7.2 percent from January 1977 compared with an average increase for all cities of 6.8 percent.

Yesterday's consumer price index for the Washington area was compiled by the Department of Labor's Bureau of Labor Statistics to coincide with publication of a new national price index, which rose 0.8 percent in January.

Culminating an eight-year project to develop more accurate consumer price data, the government has introduced a new index for "all urban consumers" to replace the previous measure of "urban wage earners and clerical workers."

The revision is particularly significant for the Washington area because the new index adds professionals, managers, technical workers, the self-employed, unemployed and retires - categories of the work force that are important to the Washington economy.

Previously, the national and area government index focused on salaried and clerical workers and government spokesmen said yesterday the revised measure accounts for 80 percent of the civilian work force while the old index represented about half that number.

To help the public get accustomed to the new index, the government will continue to publish data based on the old measurements through May. Under this previous index, the consumer price jump here in December and January was 0.7 percent - or less than the all-city average of 0.9 percent. Under the new index, the area CPI stood at 190.2 in January (1967-100); using the old index, the area CPI was 189.5.

As revised, the new all urban consumers index for Washington assumes greater spending for some items in the family budget than under previous surveys. For example, the new index assumes that all housing costs account for 46.7 percent of all spending (compared with 36 percent previously), that transportation accounts for 17.4 percent of spending (up from 13 percent) but that food and beverage spending is about 17 percent (compared with 26 percent previously).

Included in the housing portion of the consumer's dollar are mortgage and interest payments, utility bills, rent, fuel, maintenance and repairs - categories that have been soaring in the D.C. area.

In the December-January months, the government said, overall housing prices jumped 1.6 percent here, despite declining electricity charges. Since January 1977, area housing costs rose 8.7 percent compared with 7.5 percent for all U.S. cities.

Area food costs rose 1.5 percent from November to January with grocery store prices up 1.7 percent and food at restaurants up 1 percent. The annual rate of increase for grocery store prices here was 9 percent compared with 8.7 percent for all cities while restaurant prices were up 9.2 percent for the year compared with 8.3 percent for all cities.

Grocery store price increases accelerated in January after a small jump food price survey for the area also released yesterday. The January price rise was 1.2 percent compared with 0.5 percent in December, primarily because of sharp increases during January for meats, poultry, fish and eggs.

Among food store items in the past two months, prices rose for processed fruits and vegetables, beef, pork, cola and carbonated drinks and milk.Prices were down for fresh vegetables, most bakery products and sea-foods, the government said.

Area transportation costs were up 0.5 percent in December and January as higher new car prices and auto maintenance and repair costs were only partially offset by lower used car and gasoline prices.

Medical care costs here jumped 2.4 percent over the recent two months because of higher physicians' fees and hospital room rates. Since January 1977, area medical costs were up 8.4 percent compared with an all-cities average rise of 8.8 percent.

There was some good news in yesterday's report, too. Entertainment costs declined 0.6 percent because of lower prices for sport vehicles and other sporting equipment, and lower prices for men's apparel offset higher costs for women's clothing and shoes for an overoll decline of 0.3 percent.

With publication of the new all urban consumers price index for metropolitan Washington, the government now plans to issue such reports every two months instead of quarterly in previous years. New reports will be issued for two-month periods ending in January, March, May, July, September and November.