William and his wife Kate Middleton, Duke and Duchess of Cambridge, are being asked not to go to the Calgary Stampede by a European animal rights group.

A letter from the Fight Against Animal Cruelty in Europe to the royal couple, dated June 1, came to the attention of international media over the weekend.

"Rodeo is North America's bullfighting," the letter from FAACE chairman Tony Moore reads.

"The callous treatment and extreme cruelty that is involved is unbelievable."

The event, known as rodeo's richest and roughest ride, is one of the couple's expected stops on their Canadian tour, which starts later this month.

In addition to the letter, the group sent a DVD that it said shows cruelty to animals at the Stampede. Moore asks the royal couple not to attend for the sake of the animals and themselves.

When asked for a comment, royal tour organizers wouldn't confirm whether the Stampede is in fact on the itinerary.