CHANGES to Facebook's data usage rules will allow the company to share users' details with Instagram, the photo-sharing app.
Facebook included the change in a proposed update to its hefty data usage document, which said that data "from our affiliates or our advertising partners", would be used to "tell us information about you" and "improve the quality of ads."
Instagram, a photo-sharing service for smartphone users, is one of Facebook's most significant affiliates, and was acquired by the social network in October for around $715 million (£448 million).
The change will allow Facebook to build more complete profiles of its users - and target advertisements - using people's personal data from its social network and from Instagram.
Facebook has more than a billion registered users and Instagram counts 100 million devotees who use the app's distinctive "filters" to take photographs from their phones which then appear on a public feed.
In January, Google similarly said it would combine users' personal information from across its products including search, email and the Google+ social network.
Facebook's data usage document, which runs to 16 pages, also proposes scrapping a 4-year old process that had allowed the social network's users to vote on changes to its policies and terms of service.
Previously, if 7,000 comments were made on a proposed change to the site's service this triggered a vote by users who could strike down unpopular sitewide policies.
Facebook proposes to replace voting with regular Q&As with the company's chief privacy officer Erin Egan and webcasts about privacy and security.
Elliot Schrage, Facebook's vice president of communications, public policy and marketing, said the voting mechanism "incentivized the quantity of comments over their quality," as the reason for its removal.
The social network also wants to loosen the restrictions on how members of the social network can contact other members using the Facebook email system, eliminating a setting for users to control who can contact them.
The company said it planned to replace the "Who can send you Facebook messages" setting with new filters for managing incoming messages.
Asked whether such a change could leave Facebook users exposed to a flood of unwanted, spam-like messages, Facebook spokesman Andrew Noyes said that the company carefully monitors user interaction and feedback to find ways to enhance the user experience.
"We are working on updates to Facebook Messages and have made this change in our Data Use Policy in order to allow for improvements to the product," Mr Noyes said.
Jennifer O’Mahoney Telegraph.co.uk