A high publicity official with the national headquarters of the Continental Baking Co., makers of Wonder Bread, yesterday cut short a business trip in Colorado to answer charges of discrimination in Continental's Dorchester plant.

The charges have been made by the Boston Action Group (BAG), a civil rights organization committed to improving opportunities for Negroes. BAG officials claim that the Dorchester plant turned down their request that the plant hire 12 more Negroes, to bring the total number of Negro employees to 20. The plant currently employs about 200 persons, according to BAG.

In answer to the BAG statements, Anthony Corvino, personnel manager of the Dorchester plant, said, "It's all false." Corvino refused to elaborate until a statement is issued by Continental head-quarters in Rye, N.Y.

This Saturday BAG will take its first active step against Continental by staging a large protest demonstration in Roxbury. Pamphlets will be widely distributed urging Negroes not to buy Wonder Bread with the slogan "Don't buy where you can't work.

The Greater Boston Ministerial Alliance, which represents the major churches in Roxbury and the South End, has put its full weight behind the BAG campaign. From his pulpit last Sunday, Rev. George Thomas of St. Marks Church told his Roxbury congregation: "Now the people of our community must tell them that it isn't possible for Negroes to continue to buy Wonder Bread until they find it possible to hire the 12 people we requested."