The Babyshambles frontman sent his former lover a brooch with a deceased rodent attached to it, claims the Daily Star.
The rocker was apparently inspired by Hole singer Courtney Love, who gave one of her friends the same gift.
A source commented: "Some people might find it disgusting but it’s still art, if in its extreme sense. Nobody baulks when Damien Hirst puts a shark in formaldehyde and this is very similar.
"It’s become the latest outlandish fashion statement in Manhattan but Pete is trying to emphasise how he feels without Kate – defeated, crushed and broken, like the dead animal."