Amy Winehouse and Blake Fielder-Civil reportedly had a steaming row inside a toilet cubicle in Harvey Nichols over British supermodel Lily Cole.
The married couple were seen by onlookers at the London department store engrossed in a heated debate for 20 minutes.
The argument apparently started after Amy spotted Blake chatting intently to Cole at the bash.
A source told the Mirror: "Blake and Lily were chatting very intently for ages before Amy arrived.
"Amy went ballistic when she saw them together and dragged Blake to the toilet to confront him. They were arguing for at least 20 minutes. Amy was shouting at him and asking him what an earth he was doing with Lily.
"Blake tried to explain but Amy was having none of it. People waiting to use the toilets were just standing their open mouthed. Their marriage is hanging by a thread."
Amy was recently asked by Prince to visit his Minnesota home to work on some music together. He reportedly asked the singer not to bring her husband.