Shoplifting at retail stores in metropolitan Washington decreased an estimated 4.5 percent last year, but still accounts for net losses of more than $457 million annually, the Greater Washington Board of Trade said yesterday in kicking off its 14th annual anticrime campaign.

Shoplifting has decreased steadily for three years since hitting a record high of nearly $500 million in 1979-80, according to statistics compiled in the board's survey of 175 stores representing most of the region's retail sales.

"It is on the decline, but it is still an astounding amount of money," said Garry R. Curtis, manager of the board's retail bureau. "The essence of our campaign is to remind people that shoplifting is stealing . . . and it gets you a criminal record and the label of a thief."

The new campaign, with the slogan "Don't Reach for Trouble," will focus on a series of public service advertisements and an educational program aimed at schoolchildren, emphasizing the seriousness of shoplifting. Curtis said the media are expected to donate more than $1.5 million worth of advertising time and space.

The board says it believes that its past campaigns, coupled with more sophisticated means of detection, have contributed to the decrease in pilferage. An increasing number of retailers have been using closed circuit television, including "pinhole" lenses concealed in inconspicuous locations, to catch shoplifters. Many also use plainclothes detectives and electronic tags attached to clothing.

Local law enforcement officials, in statements released by the board of trade yesterday, endorsed the publicity effort and said it has proven effective in deterring shoplifting.

The thrust of the publicity effort is to remind the "basically honest people to stay honest," the board said. The anticrime campaign does not target professional thieves, but is aimed mostly at "ordinary people," according to the board, which said that the largest class of shoplifters is housewives, followed by teen-agers. The board also emphasized that most shoplifters are not poor, but rather middle- or even upper-income.

The board's data on the subject suggests that the total loss of shoplifting translates extra costs of $290 per year for each adult in the area in increased prices to make up for the losses.

The campaign runs from mid-September to Dec. 31, the period during which the overwhelming percentage of shoplifting occurs, according to the board's survey.