Germany's antitrust regulator is reportedly about to order Facebook to stop collecting certain user data.

The Bundeskartellamt has been investigating Facebook since 2016 and has already expressed concern about the way Facebook collects information on its users via WhatsApp and Instagram.

It's another warning shot for Facebook, since it marks Germany becoming even more aggressive towards the social network on user privacy.

Germany is the most powerful country in the EU, and its attitudes towards privacy may spread more widely through the bloc.

Facebook's entire business model is being challenged in Germany, which is reportedly on the verge of imposing strict new rules on what information the social network can and can't collect.

According to the German tabloid Bild, which is owned by Business Insider's parent company Axel Springer, Germany's antitrust regulator is ready to demand that Facebook stop collecting certain data, which may fundamentally alter its business.

The regulator, the Bundeskartellamt, hasn't publicly confirmed the upcoming ruling. A spokesman told Business Insider that it still plans to release its report in early 2019, but said there was nothing further to add.

In a preliminary ruling issued in December 2017, the Bundeskartellamt did indicate its thinking. The regulator said Facebook was the dominant social network in Germany, and that it was concerned about the way Facebook scoops up data on third-party services, including its Facebook-owned WhatsApp and Instagram.

Read more: Apple has reportedly hired a fierce Facebook critic after repeatedly attacking the firm's 'industrial' data hoarding

At the time, its president Andreas Mundt said: "We are mostly concerned about the collection of data outside Facebook's social network and the merging of this data into a user's Facebook account. Via APIs, data are transmitted to Facebook and are collected and processed by Facebook even when a Facebook user visits other websites."

Mundt said it wasn't clear users gave consent to this level of tracking.

Facebook suggested it wasn't the antitrust regulator's job to look into these issues.

A spokeswoman told Business Insider: "Since 2016, we have been in regular contact with the Bundeskartellamt and have responded to their requests. As we outlined publicly in 2017, we disagree with their views and the conflation of data protection laws and antitrust laws, and will continue to defend our position."

Bild said it wasn't clear how strictly the Bundeskartellamt would enforce any ruling, with the regulator more likely issuing a deadline for Facebook to comply.

Germany has been aggressive with Facebook, partly due to the nation's love of privacy

That one country is stepping up against Facebook may appear trivial, given the company has 2 billion users around the globe. But Facebook should worry both about Germany's aggressive regulatory stance, and whether its arguments convince other countries to follow suit.

One reason German lawmakers are so uneasy about Facebook is the country's own troubled history. Its Nazi past means hate speech laws are rigorously enforced, and a history of state surveillance has made people ultra-sensitive about their privacy.

Germany also happens to be the most powerful country in the EU, and its pro-privacy attitude is already being baked into legislation that applies across the bloc. It probably isn't a coincidence that a German MEP, Jan Philipp Albrecht, is described as the "father of GDPR," the strict new privacy legislation that has already cost Facebook users in Europe.

And Germany has taken a consistently aggressive stance on Facebook over the last few years.

In 2018, Germany's data watchdog banned Facebook from collecting any user data via its chat app WhatsApp. It introduced a hate speech law that gave Facebook and other social platforms just 24 hours to remove hate speech, or face fines of up to €50 million ($58 million.)

And Germany's justice minister, Katarina Barley, said in December that Facebook needed to clarify its API data-sharing deals with services such as Spotify and Netflix, which gave the companies read access to people's messages.