Chris Martin says he initially thought the Band Aid single was a "tremendously bad idea".
He says he only agreed to sing on the track after watching a report on refugees in Sudan's Darfur province reports Femalefirst.
The Coldplay singer was horrified by plans to make a Band Aid 20 version of the 1984 classic, but changed his mind when he realised Travis star Fran Healy was joining the cause, which will raise money for African famine victims.
He said: "My first reaction was that this was a tremendously bad idea, the cheesiest thing I'd ever heard.
"A couple of weeks went past and I was told Fran was doing it, which made it more interesting. Then I watched the news and saw a report on Darfur. I decided there and then that I was going to do this. I was genuinely moved."document.write(unescape("