Elton John's husband David Furnish has called Madonna "desperate" and a "narcissist."
The stinging attack came after Madonna took home the prize for Best Original Song at last night's Golden Globes and beat Elton who was also nominated in the same category.
David had immediately taken to his Facebook page when the Material Girl was announced as the winner the song Masterpiece from her movie W.E. that she also directed.
"Madonna. Best song???? F*** off!!!" he wrote. Elton had earlier said that Madonna had "no f***ing chance of winning."
But David was seemingly still seething and later continued his rant on the social networking site.
"Madonna winning Best Original Song truly shows how these awards have nothing to do with merit," David said.
"Her acceptance speech was embarrassing in its narcissism. And her criticism of Gaga shows how desperate she really is."
Elton was nominated for his Lady Gaga collaboration Hello Hello from animated film Gnomeo and Juliet.
"Oh I hope he speaks to me for the next couple of years. He's known to get mad at me," Madonna told the BBC after the ceremony. "I don't know, he's brilliant and I adore him. He'll win another award and I don't feel bad."
The two musical icons have been feuding for years when the Rocket Man slammed Madonna's win of Best Live Act at the 2004 GQ Awards.
"Since when has lip-synching been live?" he said sarcastically at the time.