'The Ballad of Ronnie Drew', performed by a variety of artists including U2, Andrea Corr, Sinead O'Connor, The Dubliners and Kila, debuts at number two in the chart.
It is followed by Glen Hansard and Marketa Irglova's 'Falling Slowly', which rises up twelve places to number three.
Basshunter's 'Now You're Gone', which was number one last week, now drops down to fourth position, while Luan Parle's 'Ghost' enters the chart at number ten.
Glen Hansard and Marketa Irglova's Once climbs up two places to the top of the album chart this week, followed by Amy Winehouse's Back to Black at number two and Michael Jackson's Thriller at number three.
The top ten singles in full:
1. (2) Duffy: 'Mercy'
2. (-) Various: 'The Ballad of Ronnie Drew'
3. (15) Glen Hansard & Marketa Irglova: 'Falling Slowly'
4 (1) Basshunter: 'Now You're Gone'
5 (3) Nickelback: 'Rockstar'
6 (9) H 'two' O ft. Platnum: 'What's It Gonna Be'
7 (7) OneRepublic: 'Stop and Stare'
8 (5) Britney Spears: 'Piece Of Me'
9 (4) Lupe Fiasco ft. Matthew Santos: 'Superstar'
10 (-) Luan Parle: 'Ghost'