Consumer prices in the Washington area rose at less than half the national rate from March to May, according to figures released yesterday by the Bureau of Labor Statistics.

While changes in the consumer price index reflected a slowdown in the nation's inflation rate, the latest trend was even more marked in the Washington area. Compared with a national change of 2.1 percent, prices in the Washington area rose only 1 percent for the two-month period. The comparison is based on data unadjusted for seasonal fluctuations.

Much of the area's lower inflation rate apparently relected regional differences in food prices, with fresh fruits and vegetables here a better bargain than they were on a national average, and a slowdown in home purchases that helped hold down the cost of shelter.

While the cost of food consumed at home actually declined 0.5 percent in the Washington metropolitan area, nationally the prices consumers paid for groceries increased 1.2 percent. The biggest difference was in the cost of fruits and vegetables, which rose 6.1 percent on a national average but dropped 0.3 percent in the Washington area, where regionally grown spring vegetables began appearing on market shelves.

The cost of home ownership increased 2.4 percent locally, compared with a 3.6 percent increase nationally. As it did nationally, the rise reflected higher mortgage costs, rent and electricity and natural gas costs.But in the Washington area, the number of housing purchases increased by less than 1 percent, while they grew by 2.3 percent nationally.

Another major difference was in the retail costs of apparel, where prices declined by 1.7 percent in the Washington area but increased by 0.9 percent nationally.

Washington-area transportation costs rose by 1.1 percent, compared with a 2.2 percent increase nationally. The increases reflected higher prices for new and used cars as well as for automobile maintenance and repairs.

Costs declined 0.9 percent for entertainment in the Washington metropolitan area, while they were increasing 1.7 percent nationally. That difference reflected, among other things, sales of sports vehicles such as motorcycles, according to a BLS spokesman.