A trade group representing independent automotive-parts importers is asking the government to investigate allegations of unfair trade practices by Japanese car makers.

"We believe that the new-vehicle manufacturers from Japan, all of which have wholly owned operating subsidiaries in this country, are currently engaged in a pernicious and predatory attempt to inflict a mortal wound on those seeking to compete with them in the United States," the trade group, Auto International Association, said in a statement released Monday.

The group, based in Whittier, Calif., said the importation and distribution of auto parts in the United States is a multibillion-dollar retail market "being threatened by Japanese auto makers."

The group said evidence of the alleged unfair trade practice "is presented by the simple fact that since January of 1985, when the yen was valued at $.00393 {254.5 yen to the dollar}, the yen has gained 74.3 percent in value vis-a-vis the dollar at its current value of .006849 {146 yen to the dollar}. During this period, however, the prices of auto parts from the Japanese new-vehicle manufacturers have increased negligibly, in the range of 12 percent to 15 percent as of April 1987."