"My experience is: Facebook only takes responsibility when it's forced to do so," Katarina Barley said in a statement, adding that the company must inform all affected users about the glitch.

The passwords, stored in readable format within Facebook's internal systems, were accessible to as many as 20,000 Facebook employees and dated back as early as 2012, cyber security blog KrebsOnSecurity, which first reported the issue, said in a report on Thursday.

(Reporting by Riham Alkousaa; Editing by Tassilo Hummel)