A Spanish Linux software group has filed a complaint against Microsoft to the European Commission over its controversial implementation of UEFI Secure Boot for Windows 8 hardware.

The Linux group Hispalinux filed a complaint with the Madrid office of the European Commission on Tuesday morning, according to Reuters.

The complaint focuses on the Microsoft's Windows 8 "certified PC" feature UEFI (Unified Extensible Firmware Interface) Secure Boot , which the group has labelled an "obstruction mechanism".

Concerns about UEFI Secure Boot for Windows 8 were raised in 2011 after Linux users questioned whether the feature would prevent dual-booting with Linux on Windows 8 machines.

At the time, Red Hat employee Matthew Garrett commented on his blog that Microsoft's move on secure boot "removes control from the end user and places it in the hands of Microsoft and the hardware vendors. The truth is that it makes it more difficult to run anything other than Windows".

More recently Linux community members have been hashing out the optimal methods to install Linux on Windows 8 PCs with Secure Boot.

Linux founder Linus Torvalds labelled suggestions that inserting Microsoft-signed keys into the Linux kernel to achieve this was "moronic" . Besides security threats, one fear is that Microsoft could arbitrarily disable the key , rendering the Linux-installed Windows 8 PC useless.

Hispalinux's complaint to the EU covers much of the same territory.

Hispalinux lawyer Jose Maria Lancho told Reuters that UEFI Secure Boot was a "de facto technological jail for computer booting systems" and that the feature was "absolutely anti-competitive".

In a blog post, Hispalinux points to what it considers potential breaches of Europe's antitrust laws and consumer laws.

Windows 8 obstructs competition by preventing any rival operating system to boot directly on the hardware, while the choice of the system on the hardware reflected an agreement between hardware manufacturers and Microsoft, not the consumer, it says.

According to Hispalinux, the agreements between Microsoft and hardware makers were prohibited under the European Union's Treaty Article 81.1 and 82, dealing with competition law, and several articles covering European consumer laws.

The European Commission is obliged to investigate any complaint it receives, and take action of any anti-competitive behaviour is found.

A spokesperson for European Union's Competition Commissioner Joaquín Almunia declined to comment on the complaint, however in January this year, the commissioner addressed questions from Swedish Pirate Party MEP Ameilia Andersdotter over whether Microsoft's UEFI Security Boot did violate European competition law.

Almunia said the Commission was aware of the Microsoft Windows 8 security requirements, but did not have any evidence suggesting they would lead to practices that violate Europe's competition laws.

"Whether there is a violation of EU competition rules depends however on a range of factual, legal and economic considerations. The Commission is currently not in possession of evidence suggesting that the Windows 8 security requirements would result in practices in violation of EU competition rules as laid down in Articles 101 and 102 TFEU. In particular, on the basis of the information currently available to the Commission it appears that the OEMs can decide to give the end users the option to disable the UEFI secure boot."

"The Commission will however continue to monitor the market developments so as to ensure that competition and a level playing field are preserved amongst all market players."

ZDNet has not received a response from Microsoft.