Katy Perry and Calvin Harris have had a very public bust-up over Twitter after the Flashback star pulled out of her UK shows. Calvin was scheduled to open for Katy’s gigs but cancelled at the last minute after being angered over set arrangements.

The furious I Kissed A Girl singer vented on Twitter, posting: ‘Calvin Harris will NOT be joining in on the fun and has CANCELLED last minute.’

To which Calvin, 27, replied: ‘Sorry to all who wanted to see me with Katy – her team suddenly moved the goalposts and I was to appear on stage with no production.’

Katy didn't believe that this was an adequate excuse, saying: ‘The goalpost seems to be perfectly fine for New Young Pony Club, Yelle, Robyn, Marina & The Diamonds, to name a few...Or how bout Janell Monae and her 16 piece band… It’s fine, I’m used to you cancelling on me, it’s become ur staple!’

Calvin then tried to explain by tweeting: ‘It would have looked s***, sounded s*** - trust me you would have been more disappointed SEEING the show than u are with me cancelling.’

Calvin thought he should compliment her, tweeting: ‘Her show is AWESOME, you’ll have an amazing time without me. (especially w/o me DJing on a cardboard box in front of a pink curtain)

But Calvin’s cancellation seemed to spark fury with Katy Perry fans also, who started sending abusive messages to the DJ.

Calvin retaliated by tweeting: ‘WTF are Katy Perry fans telling me to KILL MYSELF on twitter for? Seriously. I’m a producer making music. Leave me alone please thanks x’

Despite the twit-war, Katy still hit the stage last night at Dublin’s O2 Arena as part of her California Dreams Tour.

The star was mobbed outside her hotel yesterday by fans, with one waiting for Katy to autograph his photo of her. But the singer was no doubt disappointed with his photo choice, as he held onto a copy of the picture that Russell Brand famously posted on Twitter, of Katy without make-up.