Adele ignored Bob Geldof's Band Aid phone calls and he admits some stars "just don't want to do it".
The 'Skyfall' hitmaker was approached by the charity record's organisers and Geldof, 63, countless times but refused to respond to their efforts to get her to participate.
He told The Sun newspaper: "Adele is doing nothing. She's not answering the phone. She's not writing. She's not recording. She doesn't want to be bothered by anyone."
In spite of the efforts of the Boomtown Rats star and songwriter Midge Ure, Adele, 26, "didn't even bother" to explain her decision to turn down their offer.
A Band Aid source said: "We made 100 phone calls to Adele because Bob and Midge were desperate for her to take part. "But it was complete radio silence back. She didn't even bother to say
she couldn't do it."
The 'I Don't Like Mondays' hitmaker believes the Grammy Award-winner - who has two-year-old son Angelo with her partner Simon Konecki - is too busy being a mum.
He said: "She won't even pick up the phone to her manager. She's bringing up a family, you know. Some people just don't want to do it.
"Of course they agree with it, but it's not their way of doing something."
After seeing the turn out for this year's single - a play on the original 'Do They Know It's Christmas' to raise money for the Ebola crisis in Africa - which features One Direction, U2's Bono, Ellie Goulding and Coldplay's Chris Martin, Bob isn't sure they could have fitted any more artists in the studio.
He said: "Some people just don't think that they could make any impact at all by coming along. What can we do that will possibly make it any better?
"And frankly, if we had any more people in this room we wouldn't get it done. "It's f***ing rammed. You can't move, you know."