Aristocrat has filed a claim of breach of intellectual property law regarding its Lightning Link machine.
Lightning Link has been installed in casinos across the world and won the Land-based Product award at last year's Global Gaming Awards.
Aristocrat alleges Ainsworth stole the technology developed for Lightning Link and used it in one of its own machines.
Aristocrat said: “This case goes well beyond simple copyright infringement and concerns allegations of extensive and deliberate misappropriation of trade secrets, confidential information and intellectual property.
“Upholding appropriate standards is part and parcel of ensuring ongoing trust in our business and industry, and is an important part of Aristocrat’s high compliance culture.”
In response, Ainsworth said: "Ainsworth will be vigorously defending the claims made by Aristocrat in these proceedings."
The issue between the Australian casino suppliers has been developing since last year when Aristocrat took legal action demanding Ainsworth release documents on how it developed one of its new machines, Jackpot Strike.
Aristocrat wanted to see all Ainsworth source code, mathematical tables, game rules, artwork and commercial documents relating to the machine.