Facebook’s purchase of WhatsApp has a rocky road ahead after privacy groups teamed up to pressured US regulators to put the breaks on the $19 billion [£11.4 billion] deal.

Related: Watchdog tells users to delete WhatsApp after Facebook acquistion

Two prominent privacy groups want regulators to prevent the deal being completed until Facebook gives more details about what it will do with WhatsApp’s trove of personal data.

"Users provided detailed personal information to the company including private text to close friends. Facebook routinely makes use of user information for advertising purposes and has made clear that it intends to incorporate the data of WhatsApp users into the user profiling business model. The proposed acquisition will therefore violate WhatsApp users' understanding of their exposure to online advertising and constitutes an unfair and deceptive trade practice, subject to investigation by the Federal Trade Commission,” read a statement drawn up by the Electronic Privacy Information Center and Center for Digital Democracy, according to the BBC.

Specifically, the groups want US regulators to investigate the deal “with regard to the ability of Facebook to access WhatsApp's store of user mobile phone numbers and metadata".

A statement from Facebook that was seen by Reuters, adds “WhatsApp will operate as a separate company and will honour its commitments to privacy and security.”

Even with statements of this ilk, opponents don’t trust Facebook’s intentions and point to its amendments to Instagram’s privacy policy after it acquired the photo sharing service back in 2012.

Privacy groups in the US aren’t the only parties urging caution over the messaging service now that it has been taken over by the social networking giant. Just weeks ago Germany’s chief privacy watchdog, ULD, stated that customers should delete the app as neither service adequately conforms to European Union data protection laws.

Related: Why did Facebook pay $19bn for WhatsApp?

Facebook spent a huge $19 billion [£11.4 billion] on the messaging service that is either free or costs users a minuscule £0.60 a year to subscribe to.