Tesco has said the X-Factor effect has boosted music and DVD sales since Sunday’s final, and the grocer predicts winner Joe McElderry’s single will be the fastest-selling of the year.

The grocer said Michael Bublé, who wowed the audience with his performance on Saturday night, saw sales of his new album double week on week, while Robbie Williams was up 64%.

Susan Boyle sales were up 100% after she starred in a special show following the final. Tesco has the exclusive rights to sell her DVD, ‘I Dreamed A Dream’, which includes footage of her original audition for the X-Factor’s sister show, Britain’s Got Talent.

Michael Mulligan, Tesco music buying manager said: “The amazing X-Factor effect we have seen shows how popular the show is with our customers. ‘The Climb’ will be the biggest single of 2009 without a shadow of a doubt – and at 29p for the MP3 track, the price is anything but steep.”

Separately, Tesco has launched legal action in Ireland against Dunnes Stores, claiming about misleading advertisements. The case – in which Tesco complained about the sale price of certain goods – has been adjourned to Thursday.

According to the Irish Times, Dunnes told the High Court that Tesco’s case is “misconceived in law and unsustainable on the facts”. It said that Tesco had engaged in similar advertising to that in which it was complaining.

Tesco secured leave last Friday to serve short service of injuncture proceedings against Dunnes over three advertisements which had appeared in the national media. Tesco said Dunnes was not fairly comparing prices in those advertisements.