The band's frontman told the Daily Star that it would have been another story if the clenched bottom had belonged to a female.
"I feel happier than ever with what we're doing," Shears said. "We're all really relaxed about it. There's no other band who could get away with this stuff. Our new music was born out of going to these insane sex parties."
He continued: "The album cover is provocative and we may not sell quite as many records because of it. It wouldn't be the same if it was a woman's behind.
"I guess some people love us for who we are, some vehemently despise us."
The group recently confirmed that 'Any Which Way' will be their next release from Night Work.
"Ana [Matronic]'s solo in that song was hilarious," Shears said. "If you get all the things right in a room for her you can stick a microphone in front of her and she'll come out with the most outrageous, amazing lines in one go."
He added: "That was all one take, and totally improvised. I was having to try to keep my hysterics in check."