The hugely talented Burke's winning track has already zoomed to No.1 on the basis of download sales alone – and industry experts are predicting that she will stay there.

Burke's emotional performance on the X-Factor final night is a key factor in the extraordinary sales to date – as is the celebrated character of the song. "I certainly hope that it stays at No.1," Hot Press editor Niall Stokes comments. "It sounds like a religious song, and very appropriate to the Christmas season – but, being written by Leonard Cohen, it is far more interesting than that. As those lines about being tied to a kitchen chair suggest, it is a hugely carnal song about love, sex – and, of course, the power of music."

Meanwhile, music retailing giants HMV report that thousands of fans rushed to download the song from the hmv.com website when it went on sale after midnight on Saturday. The physical CD is scheduled for release by SonyBMG on Wednesday 17th December.

"'Hallelujah' promises to be the biggest X Factor release yet," HMV's Gennaro Castaldo comments. "The chances are that Alexandra will have the Christmas No.1 single in the bag even before her CD single officially hits the stores midweek.

"Alexandra's biggest challenge for the festive top spot is likely to come from Peter Kay alter-ego Geraldine McQueen, who releases 'Once Upon A Christmas Song' on Monday," Castaldo adds, "and from Leona Lewis and Terry Wogan/Aled Jones, who already have songs out. But the reality is that while they may sell in the tens of thousands, Alexandra will sell in the hundreds of thousands. As bookies William Hill say, it's really all about the race for the No.2 spot now."