Bieber sings on Starship Christmas CD

Justin Bieber, pictured with Starship patient Makenzie Perry, is helping to promote the hospital's festive-season album.

A secretly filmed advertisement featuring teenage heart-throb and pop phenomenon Justin Bieber will air on local TV screens this month in support of the Starship children's hospital.

The 18-year-old Bieber avoided throngs of screaming teenage girls during his whirlwind three-day visit to Auckland in July when he visited the hospital and also recorded the ad promoting the release of the Starship Christmas album for 2012.

Bieber fever caused havoc when he visited New Zealand two years ago so the young star tried to keep his visit to the hospital - his first anywhere in the world - secret, to avoid any mayhem.

He didn't have too much luck, however.

"We were speaking in code, that kind of thing, because of Facebook and Twitter and even the kids at the hospital didn't know he was going to see them," said music industry veteran Paul Ellis.

"But as it would happen he tweeted to his 24 million followers on Twitter that he was off to Starship hospital for a visit so by the time he drove from the hotel to the loading bay at the hospital, his fans were already starting to gather."

Ranked the world's third-most-influential celebrity in 2012 by Forbes magazine and with 15 million album sales to date, Bieber sings Mistletoe on the album, which Ellis said was a "stonking good Christmas CD".

He is joined by other artists including Queen, Lady Gaga, Elton John, Ronan Keating, Hayley Westenra, Michael Jackson, Maroon 5, Adeaze, the Jackson Five, Tiki Taane, OneRepublic and Lucy Lawless - all of whom have provided their recordings royalty-free to support the children's hospital.

Ellis said having Bieber's support and him leading the television campaign to promote the album was "truly incredible".

"I have been in this business for 30 years and you don't get artists just fronting up for a cause ... they don't endorse on a regular basis - they endorse things for money," Ellis said.

"But he's standing up for a charity, which is fantastic."

The album will be available on CD nationwide from November 19 through The Warehouse stores for $16, supporting music retailers and for download from www.umusic.co.nz.

Orders for the album can be made at www.starship.org.nz/music.

Teen idol

29.8m - Twitter followers
796m - YouTube views of his song Baby
47m - Facebook friends
$55m - Earnings (at May 2012)