In a front-page story, El Mundo published stills of split- second images from the Socialist video showing atomic explosions, Doberman dogs and puppets on strings, which are said to be intermingled with straightforward propaganda against the Popular Party and its leader, Jose Maria Aznar.
In contrast, the newspaper said, the video - shown on TV last Friday - tries to glamorise the Prime Minister, Felipe Gonzalez, by including shots of the 53-year-old Socialist leader spliced with others of mini-skirted young women and Miguel Indurain, the world-famous cycling champion.
Battered by a series of scandals, Mr Gonzalez' party is expected to be heavily defeated in the elections on 3 March.
Mr Aznar reacted promptly. "Assured that you, with your honesty and respect for democracy, will have been surprised too, I take it you will order an immediate halt to the circulation of so crass a video," he said in a letter to Mr Gonzalez.
Subliminal images, seen by slowing down a videotape, are banned in television commercials in many countries, including Spain, but it is not clear whether they can be used legally in election propaganda.Reuse content