Gearbox Software is to blame for the misleading marketing of Aliens: Colonial Marines, Sega says.

In documents filed this week in a class-action lawsuit to determine if the game was falsely advertised, Sega claimed that the infamous and misleading Colonial Marines gameplay trailer which sparked the lawsuit was created entirely by Gearbox.

"The 2011 E3 demo plaintiffs complain about was created entirely by Gearbox, who then represented to Sega that 'the E3 demo is indeed the bar that we should use to determine where the game engine will be’,” the documents read.

“That is Gearbox's plan and what they believe in.

"Gearbox cannot simply disassociate itself from these statements and actions."

The now-infamous trailer's visuals were of greater fidelity than those of the completed game, and it also showed gameplay not present in the final build.

According to Sega, although it had absolute discretion over the game's marketing, a contract required that it consult with Gearbox on all decisions.

It admitted that the contract also states that Gearbox was given some free reign "to generate PR hits".

However, it claims that Gearbox went rogue with the game's promotion, and that the constant leaking of game assets by Gearbox head Randy Pitchford demonstrates that he was out of control.

Part of the company’s evidence is an internal email from Sega’s Matt Eyre, which shows his exasperation at the time of the leaks. Prior to the emails, Eyre had been speaking to Gearbox about game panels being made public.

"Effectively – it's Randy doing whatever the fuck he likes,” wrote Eyre regarding the meeting with Gearbox.

“Apparently he did it twice on [Borderlands 2] also, again, against all plans and despite the fact they [publisher 2K Games] asked him not to. I think our best result here is that we have no more panel sessions."

All of these allegations directly contradict statements made by Gearbox in July, when it said that it was merely a contractor on the game, and that it had nothing to do with its marketing.

Last month Sega agreed to settle the Colonial Marines lawsuit for US$1.25 million, but Gearbox refused to take part, and is trying to have the settlement thrown out.

The next hearing is scheduled for October 29.