''It is unacceptable that the Puerto Rican flag be used by 'Seinfeld' as a stage prop under any circumstances,'' Mr. Mirabal said.

The Bronx Borough President, Fernando Ferrer, who is Puerto Rican, said the ''Seinfeld'' episode ''crossed the line between humor and bigotry.'' Mr. Ferrer said it was a slur to depict men rioting and vandalizing a car and suggesting that it happens every day in Puerto Rico.

NBC said it was sorry if anyone was insulted by the show's humor.

''We do not feel that the show lends itself to damaging ethnic stereotypes, because the audience for 'Seinfeld' knows the humor is derived from watching the core group of characters get themselves into difficult situations,'' the network said in a statement.

NBC's president, Robert Wright, added, ''Our appreciation of the broad comedy of 'Seinfeld' does not in any way take away from the respect we have for the Puerto Rican flag.''

Mr. Mirabal also said he was insulted by the depiction of parade spectators as insensitive and of Hispanic characters ''dressing in clothing that has not been worn in 40 years.'' He wrote to Mr. Wright last month, before he had seen the show, to express his concern and to suggest that NBC have Hispanic consultants review the program for offensive content. Until that point, NBC had said only that the episode would be titled ''The Puerto Rican Day Parade.''