X Factor boss Simon Cowellis on the warpath after Robbie WilliamsandGary Barlowchose to perform on rival BBC show Strictly Come Dancing.

The pair have announced they will sing their duet, Shame, on Strictly’s first live weekend on October 2. Rob and Gary performed together for the first time in 15 years at the recent Help For Heroes concert, but Strictly Come Dancing will be the first live TV performance of the track.

Simon is reportedly far from happy, because Take That had already been lined up to perform their comeback single, The Flood, on an X Factor live show. “It is a first, but essentially they are two different acts. It should boost ratings,” an ITV insider told The Sun.

It has made Cowell more determined than ever to beat Strictly in the ratings war. “This was like waving a red flag in front of a bull for Simon. He's a perfectionist, he wants to be the best and he hates to lose.”

But it sounds like Strictly bosses are welcoming the challenge. “Getting Robbie and Gary on is just the start of an incredible series we've got planned,” a BBC source said. “We are more than ready to show what we're made of.”