Australia's New South Wales (NSW) State Police confirmed on Monday that the chief sniper involved in the 2014 Lindt Cafe siege has filed a civil lawsuit against the force.

According to News Corp, the sharpshooter who can only be identified Sierra 3-1 for legal reasons said in a 30-page affidavit that he had suffered "psychological trauma due to decisions taken by his superiors during the siege."

The officer alleges, he, along with other colleagues, were "prevented from doing their jobs" and that the lives of the hostages that were killed could have been saved.

Occurring in the heart of Sydney at a busy coffee shop, 17 hostages were taken by a crazed gunman in a terrifying 16-hour siege that saw three people killed including the gunman.

Criticized in a 2017 NSW Coroner's report, the findings concluded that the police waited "too long" before entering the building and attempting to rescue hostages.

While the force has confirmed the civil case, a spokesman for the NSW Police said "as it is before the court it is inappropriate to comment at this time."

The case is expected to be heard in a one-day hearing on April 12 next year.