The cartoon, by Peter Brookes, showed Gromit pinned against the wall with a boot mark on his back, while Miliband insisted he was "completely relaxed" about criticism from his brother, David. The latest cartoon was published "with continuing apologies to Aardman".
Park, who based Wallace on his old English teacher, last year reassured staff, when asked if he wanted the issue "knocked on the head", that he was flattered by the satirical sketches. But an Aardman spokesman said the issue would be raised again this week, adding: "You have to protect the brand."
Brookes told the Independent on Sunday: "Miliband is being seen as hapless, and that fits the Wallace character."
A spokesman for Miliband declined to comment.
- Independent