U.S. singer Lady Gaga performs at the Monte Carlo Grimaldi Forum in Monaco, February 17, 2009. [Agencies]

Lady GaGa was left red-faced when a male fan asked her to sign his genitals.

The 'Poker Face' singer was lost for words when the cheeky admirer made the X-rated request after she had performed a show in Canada.

She said: "I feel embarrassed saying this but the strangest thing I ever autographed was a man's penis. "I was doing a meet and greet backstage in Canada. I had enough room to write Lady GaGa but I don't really remember. I was laughing so hard I could barely breathe.

Maybe it is still there - who knows? It was a permanent marker too!"

The 22-year-old star recently admitted she isn't keen when the opposite sex approach her and try and flirt.

She is quoted as saying: "I don't give them a chance to even try a chat-up line. I give them a good, firm, 'No!' before they even speak. I find that does the trick every time."