Christine Lagarde, the President of the European Central Bank, said that people shouldn't be speculating on them with their life savings because they are based on nothing.
Lagarde told Dutch television that she is concerned about people who have no understanding of the risks and who will lose all.
The comments come at a time when the digital currencies are down 50% from their peak. The asset class is under scrutiny from regulators worried about the dangers it may pose to the broader financial system.
Lagarde said she was skeptical of the value of the digital currency, contrasting it with the project that may come to fruition in the next four years.
She said that it is worth nothing and there is no underlying asset to act as an anchor of safety.
I will guarantee that the central bank will back the digital currency when it is out.
Other officials have voiced their concerns. One is Executive Board member, who said in April that the new asset class were creating a new Wild West and similar to the 2008 mortgage crisis.
Lagarde doesn't hold any of her own assets because she wants to practice what she preaches.