X Factor winner Leon Jackson is headed for the Christmas number one spot, according to the latest sales figures.

Leon's cover of When You Believe - the 1998 Mariah Carey/Whitney Houston duet - is only officially released in stores today, but fans have been able to download the ballad since Leon's victory was announced on Saturday night.

On the strength of downloads alone, Leon is already the UK's best-selling single of the week, ahead of the current number one - a duet between Katie Melua and the late Eva Cassidy - and the biggest-selling single of the year, Bleeding Love from last year's X Factor winner Leona Lewis.

Though a third consecutive X Factor Christmas number one is expected, the recent furore surrounding the Pogues' 1987 classic Fairytale of New York could see some increased downloading.

BBC Radio 1 attempted to censor the song yesterday only to be forced into an embarrassing climb-down after thousands of people complained.

And according to current sales figures, other festive classics such as Mariah Carey's All I Want For Christmas Is You, Wham's Last Christmas and Merry Christmas Everyone by Shakin' Stevens could mount a late charge for the yuletide top spot.

HMV spokesperson Gennaro Castaldo commented: "Even at this early stage it looks like being Leon all the way unless, of course, the campaign to get behind the likes of The Pogues or Mariah Carey really takes off over the next few days to create one of the biggest surprises in UK charts history."

He added: "It's a real long shot, but if more and more people start downloading, say, Fairytale of New York, who's to say it can't happen - even Leon agrees that 'there can be miracles when you believe' ".

Leon is expected to sell between 250,000 and 300,000 singles in the next four days.

However his win has been tarnished amid claims that the ITV1 talent show was allegedly fixed, after viewers reported being unable to vote for show favourite Rhydian Roberts as phone lines were consistently engaged.

19/12/2007 15:37:20