The judge said the couple need to be professional and he will be scoring them on their dancing alone.
Speaking to the Daily Mail, he said she should have put a stop to it and added: "It's her job not only to protect her own relationship, but to protect the celebrity's and be the mentor".
"I think she broke protocol over that. She shouldn't have allowed it to happen". Seann and Katya apologised on Wednesday evening's It Takes Two, with Katya confirming that her relationship with Neil is fine, telling Zoe Ball: "Obviously I apologise, and I can't apologise enough to everyone who it hurt and involved".
The pair apologised after being caught kissing in public - comedian Seann had a girlfriend and Katya is married to another dancer on the show.
Will they get voted off?
So far in the competition, Seann and Katya have avoided the bottom two altogether, and last week reached their highest score by far, bagging 30 points from the judges, landing them in fifth place on the night.
She said they will be under "lots of pressure", adding: "At the end of the day, they are hired to do a job, they are both under contract, and they have to perform and the show is about dancing, it isn't about personal lives, so they have to go out and I hope they'll perform their best tonight, and if they will be eliminated, let it be".
Craig Revel Horwood appeared on the Jonathan Ross Show and said: "My take was keep them in the show, make them do the Dance of Shame, if you like".
"They are performers at the end of the day, and they have to put all of this aside, and let's face it, there are much more hard situations... last year, Alexandra Burke danced and her mother passed away, and I'm sure that was a real, real struggle to get herself together".
Seann and Katya will dance the Charleston this weekend, but it was reported that they were originally supposed to perform a rumba.
"I don't know how they're going to resolve it in their relationships but it's their business and they must do that". You don't go anywhere else, you don't do anything else'.
Do you agree with Craig?