The Forgetting Sarah Marshall star has been romancing the singer since they met backstage at last month's MTV Video Music Awards, with Brand reportedly admitting he fell "in love" with Perry during their recent holiday to Thailand.
But the I Kissed A Girl hitmaker has been warned not to expect a longlasting relationship from the British Lothario by his former bed partner Georgina Ballie, who was at the centre of his controversial prank calls to British actor Andrew Sachs last year
She tells Life & Style magazine, "Everyone knows you don't date Russell Brand seriously.
"Russell likes the idea of having a serious relationship, but when you've got all these different flavours of ice cream offered to you on a plate, you're not going to stick with vanilla, are you? I don't think he's capable of monogamy."
Brand was forced out of his BBC radio job last year after he left "grossly offensive" messages on TV star Sach's answering machine during a live broadcast with Jonathan Ross, in which the pair discussed Brand's fling with Ballie - Sach's granddaughter.