The latest suit, filed in the US District Court in Los Angeles, and separate to the current retrial happening in the Federal Court in Santa Ana, accuses Mattel of unfair business practices and anti-competitive conduct.
MGA alleges that Mattel tried to freeze out its Bratz fashion dolls after they began crippling sales of Barbie. It also accuses Mattel of infiltrating its showrooms, rearranging Barbie and Bratz retail displays, intimidating and threatening licensees and paying retailers not to buy Bratz or MGA products.
"The purpose of Mattel's anti-competitive conduct, specifically monopolising and attempting to monoplise the fashion doll market, was to eliminate or suppress the competition, mainly MGA, and effectively deprive fashion doll purchasers of the choice of buying from a Mattel competitor, including MGA," says the suit.
It continues: "Accordingly, Mattel's conduct has served to reinforce its fashion doll monopoly, and to impair the ability of MGA and others to compete in the relevant fashion doll market. Consumers are effectively deprived of choice and price competition."
Mattel lawyer Mike Zeller responded, saying: "These same arguments have been repeatedly rejected as irresponsible by the Court. This is nothing more than an end run against these prior decisions."
Separately, a retrial is underway in federal court in Santa Ana in the copyright infringement suit between the two companies over who owns the rights to Bratz.
Mattel alleges that MGA infringed on its copyrights and stole trade secrets after Bratz creator and former Barbie designer Carter Bryant took the idea for the Bratz dolls to MGA after he quit Mattel.