MadonnaMadonna has explained why she got Justin Timberlake to drop his pants for an injection of vitamin B12 while the pair were working on her new album, ‘Hard Candy’.

Earlier in the month at the Rock and Roll Hall of Fame ceremony honouring the singer, Justin revealed she administered the jab and complimented him on his bum - but she insists it wasn’t all just a plot to see Justin’s SexyBackside.

She told told New York’s Z100-FM on Thursday: “The reason I gave him a B-12 [shot] is because we only had a certain amount of days in the studio and I didn’t want him to use that as a lamea** excuse not to come to work.”

“Okay? It’s got nothing to do with butt. I promise you. Listen, I don’t need to give him a shot to see his butt. Duh.”

Justin also appeared to label his ex-girlfriend Britney Spears a “wannabe” during his introduction of Madonna at the ceremony but Madonna is herself a fan: “I actually love Britney Spears’s new album. I usually work out to her record. I do a combination of pilates and dance aerobics.”