WhatsApp will allow brands to message users as it opens data sharing with Facebook

WhatsApp will start sharing user data with Facebook following significant changes to its privacy policy which will also allow businesses to send messages to users.

The messaging app has said it will "coordinate" more with its parent company Facebook to do things like track basic metrics about how often people use its services and better fight spam on the platform.

To do this, WhatsApp will loosen some of its restrictions around user data and give Facebook access to some limited information, including users' phone numbers. The company has said this is so Facebook can offer better friend suggestions and show subscribers more relevant ads.

According to the firm, the changes also mean SMS text messages sent from companies, such as flight alerts from airlines, can now be sent on WhatsApp instead.

"We want to explore ways for you to communicate with businesses that matter to you too, while still giving you an experience without third-party banner ads and spam," it wrote in a blog post.

"Whether it's hearing from your bank about a potentially fraudulent transaction, or getting notified by an airline about a delayed flight, many of us get this information elsewhere, including in text messages and phone calls. We want to test these features in the next several months, but need to update our terms and privacy policy to do so."

WhatsApp clearly anticipated some negative reactions to the move, preempting any criticism it may face around privacy issues, by saying: "Even as we coordinate more with Facebook in the months ahead, your encrypted messages stay private and no one else can read them.

"Not WhatsApp, not Facebook, nor anyone else. We won’t post or share your WhatsApp number with others, including on Facebook, and we still won't sell, share, or give your phone number to advertisers."

The changes mark the first time WhatApp has changed it privacy policy since it was purchased by Facebook in 2014.

Facebook itself has recently made tweaks to its Messenger chat app in an attempt to make it a more hospitable place for brands by extending their ability to harness standard chat bot ads through the service.