PRINCESS Mary is renowned around the world for her sense of style, but yesterday she made an fashion faux pas of the worst kind.

The Aussie-born Danish royal stepped out in a dress which had already been seen twice on the same red carpet just a month ago.

Actresses Christina Applegate and Rachel Griffiths wore the exact same dress to a function on September 20.

Applegate later labelled the dress disaster her "worst nightmare'' when she appeared on a TV talk show.

"We're laughing and inside we're sobbing,'' Applegate told Ellen DeGeneres.

"Just a horribly embarrassing thing, because we're sitting five feet away from each other.''

Princess Mary was obviously unaware of the controversy when she stepped out in the dress yesterday.

The royal, who is patron of the Danish Refugee Council, wore the wrap dress to an event in Copenhagen marking the 50th anniversary of the Hungarian uprising.

But perhaps she can be forgiven, seeing that the Danish Court confirmed last week that she is expecting her second child.