The representative, who was not named, says the double comes in during the part where Hannah Montana does a duet with the Jonas Brothers on "We Got The Party."
The body double appears 1 to 2 minutes before the end of the song so Hannah Montana can go backstage and transform into Miley Cyrus.
The representative says other than this part, Cyrus performs both parts live.
The rep responded after OK! ran a story about fans complaining that the body double was not very convincing and they had paid big money to go to the concert.