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Google is unfairly forcing third-party Android app stores onto the sidelines in favour of its own Google Play store, according to European app provider Aptoide.

The third-party app store -- which is based in Lisbon, Portugal -- has lodged an antitrust complaint with the European Commission, the executive arms of the European Union tasked with upholding treaties and proposing new laws.

Downloadable apps are a huge part of Google's Android mobile operating system for smartphones and tablets, with Google's own Play store providing the most visible way to access this world of apps on most mobiles. The new complaint says that third-party stores -- Android app markets offered by companies other than Google -- are getting unfairly pushed aside.

"We believe that our case is strong." Aptoide co-founder and CEO Paulo Trezentos

"The European Commission has been very active in detecting situations of abuse of a dominant position," Aptoide co-founder and CEO Paulo Trezentos told CNET. "We believe that our case is strong and that can help the EC to work with Google to correct these practices."

Specifically Trezentos says Aptoide, which boasts 6 million monthly active users and generates more than 50 million downloads per month, has four key issues with the way Google handles third-party app stores.

Firstly, the process of installing third-party software on Android, which Trezentos says has been altered over time in a way that makes it "more difficult to the user to install software from anything [other] than Google Play."

The second complaint, Trezentos says, is that Google has removed core features from the Android Open Source Project and bundled them with its own Google Mobile Services packages, which includes major Google Android apps such as Maps, Gmail, and Google Play.

Trezentos says he dislikes the "removal of other App Stores, or apps with references to other App Stores, from Google Play", also alleging that Google tools such as the Chromium open source Web browser block access to third-party app stores.

"App Stores can be very interesting and Google is assuring that it controls 100 percent of that Apps distribution channel," Trezentos said. "Using anti-competition practices, it not only harms the consumer that will have fewer and more expensive options, but also the Android platform as a [whole]."

At the time of publication, Google had not responded to a request for comment. We will update this report when we have more information.

What does fairer behaviour look like?

"In the short term," Trezentos says, Google should "allow other app stores to be available in Google Play, giving the option to the user." The Aptoide CEO also wants major alternative app stores to be classified as "trusted sources" in the Android OS. Longer term, Trezentos wants Google to be "more open to the contribution of other companies to the Android platform."

Aptoide says it met with the European Union Directorate General for Competition before filing the complaint earlier this week, but hasn't had any contact since the complaint was delivered. The European Commission confirmed to CNET that it has received the complaint.

The European Commission's antitrust procedures note, "A dominant company has a special responsibility to ensure that its conduct does not distort competition", though it remains to be seen whether the complaint will proceed or force Google to change its stance.

"This will depend on the specifics of the case," Doctor Orla Lynskey, assistant Professor in law at the London School of Economics said. "Google has a position of market power on many of the potentially relevant markets and therefore the question will be whether it has taken advantage of this position in order to exclude other potential competitors from the market.

"Whatever it decides," Lynskey added, "the Commission will need to fully consider this complaint as any decision it reaches will be subject to an appeal. If it decides to continue, it will launch an official investigation into Google's practices."

Google has been lumbered with a number of antitrust complaints in Europe over the past few years. In 2013, the EU began examining Google's use of Android, which a group of companies including Nokia, Microsoft, and Oracle labelled "a deceptive way to build advantages for key Google apps in 70 percent of the smartphones shipped today."

There's no question that the Android platform enjoys extraordinary visibility in Europe. Kantar figures for the first three months of this year estimated that Android has a 72.4 percent market share in the region.

Google isn't the only company to put its own app store front-and-centre however. "The mobile market is today quite unlike the PC, because app stores are tightly integrated into each of the leading operating systems -- Google's Play store on Android, Apple's App Store on iOS, and the Microsoft store on Windows Phone," Ian Fogg, mobile analyst at IHS, told CNET.

"Should regulators choose to investigate pre-installation of alternative app stores on Android smartphones and then uphold this complaint," Fogg continued, "this will likely be the first step in a wider analysis of the whole smartphone content and services market and the role of Google, Apple and Microsoft."

While it seems a long way off at this stage, the European Commission's decisions could potentially have far-reaching consequences. "Regulators have the ability to up-end the entire current distribution model for apps, mobile content and services," Fogg notes.

As well as acting as a third-party app store, Aptoide also offers partners the option of setting up their own app stores using the company's technology. Its CEO Trezentos said that it has created "multiple reports" over the last six weeks with Google about Aptoide being blocked by the Chromium browser, but hasn't received a reply from the search giant.

Trezentos says he has "tried to find a contact point at Google to discuss the other issues but with no success so far."