Víctor García de la Concha made the comments to reporters after giving a presentation on Tuesday at the Centre of the National University of Distance Education (UNED) in Cáceres.
The 79-year-old is a former head of Royal Spanish Academy, the world's leading regulator of the Spanish language.
He now leads the Cervantes Institute, the world's largest organization for promoting the study and teaching of Spanish language and culture.
The linguist lauded Spanish as "an energy, an activity" as well as "something of a street language" that is "therefore always changing," according to national daily El Confidencial.
"We cannot think only of the language as it was for Cervantes, Calderón or Jovellanos, since language is constantly making moves back and forth by itself and in relation to itself," he asserted.
But he followed up with a swipe at the current state of Spanish as it is spoken today.
"We use it poorly, because we use little vocabulary, which impoverishes thought and expression, and we do it because we care little about the nuances of construction – not just to be correct but to have a greater ability to express oneself," he complained.
He noted that the rich linguistic heritage of Spanish was not reflected by the use that some sectors of society made of it.
"In a sense we are in a none-too-favourable time because we live in a predominantly audiovisual civilization and because sometimes it becomes fashionable to speak badly."
This is not the first time that García de la Concha has grumbled about the current state of the Spanish language.
In a 2004 interview he said: "These days many young people can barely construct a simple sentence."
His views had not appreciably softened by 2012 when he told reporters, "There is a great deal of neglect in the manner of speaking; we are in a rather shabby period."