Louisa Johnson
Louisa Johnson could be crowned the winner of The X Factor 2015 on 13 December YouTube

She has not been crowned the winner yet, but X Factor contestant Louisa Johnson is already a favourite to take the Christmas number one. Bookmaker Ladbrokes predict that the 17-year-old will top the UK chart with the X Factor winner's single, which is yet to be revealed.

According to the bookies' odds, Johnson is the frontrunner ahead of fellow X Factor contestants Reggie N Bollie, who will also compete in the ITV series' finale weekend beginning on 12 December 2015. Johnson's appearance in the final was originally shrouded in doubt after the singer cancelled a performance in Liverpool due to illness.

However, an X Factor spokesperson told the BBC: "Louisa has been sick and was ordered on voice rest yesterday, so her homecoming performance unfortunately had to be cancelled at the last moment. We do expect her to be well enough to perform in the final though."

Threatening to steal Johnson's glory are the NHS Choir who are hoping to reach number one with their Christmas charity single, A Bridge Over You, which is a mash-up cover of Coldplay's Fix You and Simon and Garfunkel's Bridge Over Troubled Water.

Listen to the NHS Choir's Christmas charity single Bridge Over Troubled Water:

Cementing what has been an incredibly successful return to music, pop star Justin Bieber is also a hot contender for Christmas number one with his odds at 7/1. The Canadian singer has released several hit singles throughout 2015 including Sorry, What Do You Mean and Where Are U Now, all of which feature on his new album Purpose.

Ladbrokes have also placed US band Eagles Of Death Metal at odds of 10/1 following the online campaign to get the group's cover of Duran Duran's Save A Prayer to the top spot in light of the Paris attacks.

The Christmas number one will be announced on Christmas Day (Friday 25 December 2015) on Top Of The Pops and the BBC Radio 1 chart show.

Ladbrokes odds for Christmas number one:

Louisa Johnson: Evens

NHS Choir: 6/1

Justin Bieber: 7/1

Reggie n Bollie: 8/1

Star Wars Theme: 8/1

Grace: 9/1

Eagles of Death Metal: 10/1

Kylie Minogue and James Corden: 12/1

Adele: 16/1