Sir Lucian Grainge finds it absolutely RIDICULOUS that Drake says he was behind a scheme to hurt one of his biggest artists when the label released Kendrick Lamar's "Not Like Us" diss track ... the Universal Music Group CEO's says he's got way bigger responsibilities as head of the company,

In a declaration letter filed Thursday night in the Southern District of New York, Grainge said Drake's accusation that UMG (parent label firm to both Drake and Lamar) defamed him “makes no sense.”

In new legal filings, the top executive has made his first public statements on the rapper's unprecedented lawsuit against his own label