"He wants it recorded that he hasn't smoked anything.
The whole affair has hit him hard. The boy is a real sportsman. He is 21 and still lives with his parents."
Using cannabis is legal in the Netherlands and the drug is not on a list of the Dutch FA's banned substances.
Smolarek was a strong candidate for the Polish World Cup squad until he was injured last month.
National team coach Jerzy Engel has said he will give the player every chance of proving his fitness, but was not optimistic.
"Unless doctors give me assurances he will be in perfect health in June, I will have to substitute him," Engel said.
Feyenoord, without Smolarek, meet Borussia Dortmund in the Uefa Cup final in Rotterdam on Wednesday.