The Sun says Berbatov, 27, signed the shirt at Sofia Airport as he set off for Bulgaria's friendly in Bosnia-Herzegovina where he scored twice in a 2-1 win.

An onlooker said: "I was gobsmacked when he took the shirt and signed it.

"He didn't have any problems with it at all.

"If I was one of Berbatov's team-mates or a fan, I'd be furious. It is incredibly disrespectful - he may as well have kissed the United badge."

Spurs legend Jimmy Greaves said: "Signing the United shirt is certainly cheeky.

"He clearly wants to leave. If he doesn't want to stay they should get rid of him."