The Irish rockers teamed up with bosses at tech giant Apple to make Songs of Innocence available for free download to half a billion users, but the move almost backfired when a glitch meant the record was automatically downloaded to some clients' playlists.

The fallout from the incident threatened to derail the band's promotion of the new album as critics raced to slam them for the stunt, prompting drummer Mullen, Jr. to insist he didn't "give a s**t" about the complaints.

However, he has now revealed he had grave misgivings about the release format and is glad to see the band has finally ridden out the storm.

Mullen, Jr. tells Q magazine, "Was I uncomfortable with it? Yeah, at times I was. Afterwards I was particularly uncomfortable. S**t happens... (But) all of a sudden the ship is off the sandbank. We're floating again."

U2 frontman Bono also repeated his belief the rockers made mistakes in the way they handled the album release, adding, "Giving people a free gift, it's hard to get it wrong. But we could have explained the intention behind it and we didn't. That was a big mistake."