The spokesperson said: "I have spoken to Jermaine and he said it is untrue."
Spanish paper Marca had claimed that his former club Real Zaragoza had to get in touch with him this week to tell him about the car.
The paper claimed that when Pennant was contacted by Zaragoza about the car, he admitted he did not remember anything about it.
Marca also said that Zaragoza were then forced to open the car and were surprised to find that the keys were on the seat.
Pennant is a big fan of cars and has a sportscar collection.
During his spell in Spain he infuriated coach José Aurelio Gay after turning up late for training three times in the space of two weeks.
Last August he signed for Stoke City on a four-month loan deal which was then made permanent in December.
Pennant was once deemed one of the hottest prospects in the game, and played 24 times for the England U21s, but the 28-year-old has never won a full England cap.