Washington area retailers lost nearly $400 million of merchandise to shoplifters and internal thieves between Aug. 1, 1976, and July 1 of this year, according to a business community survey.

Although the recent losses were an estimated 2 per cent higher than the previous comparable period, the rate of increase in retail theft has been slowing down for several years, a pattern reflected in general crime statistics.

With one of the worst records of retail theft in the country by the early 1970s, metropolitan area officials launched what has become one of the most extensive annual campaigns in any urban area, aimed at stopping growing losses.

Theft at some stores here has been exceeding 5 per cent of sales volume, eating into business profitability and leading to increases in consumer prices.

The Metropolitan Washington Board of Trade, which has launched a campaign with area police officials to curb shoplifting, provided the following figures on total retail theft in recent years.

"These are numbers, but real terms - people terms - such losses have been a contributing factor in forcing many retailers to go out of business in the metropolitan Washington area," noted Charles L. Huntley, director of community affairs here for Sears, Roebuck & Co., and chairman of the Board of Trade's anti-shoplifting campaign.

Specifically, former officials of the defunct Kann's and Lansburgh's department stores have cited increased theft as among the factors which caused their business to deteriorate.

According to Board of Trade survey data, teenagers and housewives are the two largest groups of shoplifters, accounting for 33 per cent and 28.3 per cent of all shoplifting apprehensions, respectively.

Retail officials say they do not have precise data on how much merchandise actually is lifted by shoppers and how much is stolen by company employees.

But, according to Leonard Kolodny, manager of the Board of Trade's retail bureau, internal thievery accounts for a larger dollar amount than stealing by shoplifters. At the same time, a larger number of shoplifters than store employees are apprehended, with each person stealing a relatively small amount.

Items most popularly stolen are clothing and phonograph or tape recordings, according to local merchants. Weekdays and evenings are the most active periods for shoplifting, and 13.4 per cent of shoplifters apprehended in the recent years here were in the top income brackets.

More than half the shoplifters arrested had incomes in a middle range and 35 per cent were among the lowest income groups. More than 62 per cent of the shoplifters were high school graduates.

According to D.C. Police Chief Maurice J. Cullinane, shoplifting accounted for 8.6 per cent of reported larcenies in 1976. He noted that larcenies in 1976. He noted that larcenies equal about 50 per cent of total reported crime in the city, making the shoplifting figure "impressive and a great source of concern."

A goal of this year's campaign to halt shoplifting - described as "a game for losers" in Board of Trade posters and advertising - is to convince potential thieves that they will be prosecuted.

For example, Prince George's County State's Attorney Arthur A. Marshall Jr. said shoplifting "has fast become a major crime," with county retail theft soaring nearly 65 per cent from 1973-74 to 1976-77.