The notice said the “Office of Cybersecurity has deemed WhatsApp a high risk to users due to the lack of transparency in how it protects user data, absence of stored data encryption, and potential security risks involved with its use.”

The memo, from the chief administrative officer, recommended using other messaging apps, including Microsoft Corp’s Teams platform, Amazon.com’s Wickr, Signal, and Apple’s iMessage and FaceTime.

Meta disagreed with the move “in the strongest possible terms”, a company spokesperson said, noting that the platform provides a higher level of security than the other approved apps.

In January, a WhatsApp official said Israeli spyware company Paragon Solutions had targeted scores of its users, including journalists and members of civil society.

The House has banned other apps from staff devices in the past, including the short video app TikTok in 2022 due to security issues.