Perry, 27, whose divorce from comedian Russell Brand was finalised in July, is said to have told the 'Half of my Heart' singer to lose her number because he cannot commit, reported Radar online.
"John just can't commit, and he kept luring Katy back with promises that was going to change, but then he didn't. Katy was pretty crazy about him, so she kept giving him another chance," a source said.
"John liked Katy, so he wanted to keep her in his life, but it just wasn't up to Katy's standards. She needs the guy to be on board 100 percent and she was sick of John disappearing for five days at a time. Finally she was like 'lose my number'," the source added.
The on-off couple first began dating in early August but split after just two weeks with friends saying it was only a casual rebound romance following her divorce from Brand.
The pair reconciled a few weeks later but this time they have split for good.
Perry is preparing to host a divorce party later this month on what would have been her second wedding anniversary on October 23.