James Martin/CNET

Edward Snowden has joined a growing group of privacy experts criticizing Google for not integrating end-to-end encryption as a default feature in its new Allo messaging app. In a tweet the NSA whistleblower called Allo "dangerous" and warned his followers against using it.

Allo has an incognito mode that promises end-to-end encryption through the popular Signal messaging protocol, but it has to be manually switched on for specific conversations. And to use Allo's Smart Reply feature, which allows the app to read your messages and suggest possible replies, you'll have to disable incognito mode completely.

Allo, which Google announced at the I/O developer conference this week, is Google's answer to messaging apps such as WhatsApp and comes with added personal-assistant features. WhatsApp also uses Signal for encryption, but Signal is baked into the app for all conversations from the start.

Google didn't immediately respond to a request for comment.