Fusari launched a lawsuit against GaGa earlier this week on the basis that the singer has allegedly denied him his share of song royalties and merchandising revenue.
But in her counter-claim GaGa alleges that the producer exploited her and induced her into an "unlawful arrangement" to pay him 20 per cent of her royalties.
She is now seeking a Manhattan court order declaring their contract void – and she wants any cash he’s already received back.
Fusari meanwhile acknowledges that he has received £403,000 from GaGa, but insists that’s a fraction of what he is owed.
We sense this legal battle could just keep on going on and on!