UEFA confirmed this afternoon [Friday] they were taking disciplinary action against the Arsenal striker, who dropped his shorts below his waistline and hoisted his shirt after scoring twice in Wednesday's Group B match in Lviv.
European football's governing body said in a statement: "UEFA has today [Friday] announced that disciplinary proceedings have been opened against Denmark's Nicklas Bendtner for improper conduct (Law 4 of the Laws of the Game) at the UEFA EURO 2012 Group B match against Portugal in Lviv on Wednesday 13 June.
"The UEFA Control and Disciplinary Body will deal with this case on Monday."
Bendtner has already been reprimanded by the Danish Football Association, despite claiming he had no idea he had broken any rules by revealing the Paddy Power branded boxer shorts.
He said: "It is just a pair of lucky boxer shorts that I used in the first game as well and have used before the tournament.
"I didn't know I was breaking any rules but I am aware of that now."
Paddy Power congratulated Bendtner on his actions on the night of the game.
The bookmakers' Ken Robertson said: "I'm truly delighted for Nicklas, what a stunning performance tonight [Thursday].
"I've no doubt that the luck of the Irish thanks to our lucky underpants helped him find the back of the net twice!"
The Danish FA, who are sponsored by rival bookies Ladbrokes, said: "We have spoken to the player and he will not play in those [underpants] against Germany on Sunday."
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