Rockers U2 have hit back at critics who lined up to slam the band over its Apple album release stunt, insisting they will not "lose sleep" over the uproar.

The Beautiful Day hitmakers sparked controversy in September (14) after striking a deal with the tech giant to make their new record Songs of Innocence available for free download to half a billion Apple users.

The move almost backfired when a glitch meant the album was automatically downloaded to some users' playlists, prompting frontman Bono to apologise for the blunder during a question and answer session with fans on Facebook.com the following month (Oct14).

However, they have now come out fighting over the furore, with Bono issuing an "apology for the apology" and drummer Larry Mullen, Jr. insisting he doesn't "give a s**t" about the band's online critics.

The singer has even branded the controversial stunt "one of the proudest moments" in the group's career.

Referring to the technical glitch that left some Apple users with the album in their playlist whether they wanted it or not, Bono tells Mojo magazine, "I mean, come on. Of the great crimes against mankind...? This is an honest mistake, and we're just not going to lose sleep about it... What I'm saying is that of the mistakes that are being made on the interweb, and there are some grave and gross violations, is this so bad? And if this was a Steven Spielberg film, would there have been the same fuss?...

"I'm already working on the apology... for the apology. Because I'm very proud of what we did. It's one of the proudest moments in U2's history. I was apologising to a young woman on Facebook, who thought we were rude. That's all."

Mullen, Jr. adds, "I don't give a s**t if you don't like U2. So you can type? Well done. Get over it."