Simon Cowell
X Factor boss Simon Cowell has revealed the exciting changes to the format for series 12 (Reuters/Phil McCarten)

The X Factor will be returning to screens on 29 August with a revamped format. Ahead of the series 12 premiere, show boss Simon Cowell has previewed what viewers can expect from the auditions process and the brand new development for judges' houses.

Perhaps the biggest change to the long-running ITV singing competition will be the judges' houses stage, which will see viewers decide which batch of contestants are grouped with the judges, Cowell, Cheryl Fernandez-Versini, Rita Ora and Nick Grimshaw. In previous series, the judging panel were usually told by Cowell, 55, whether they would mentor the girls, boys, group or overs.

Viewers will be able to vote via Twitter from 29 August by hashtagging the name of the judge they choose and the category they would like them to mentor. Votes close on 1 September at 12noon. The judges will learn which category they have been given during the six-chair challenge which will be filmed at the SSE Arena in Wembley.

Watch The X Factor series 12 promo:

Speaking about the new format, Cowell said in a statement: "Interestingly, there's no weak category this year. I can see who the winner of each category could be. It could all change, we've only seen them for the first time, then the second time we see them they could be terrible. So we'll see."

Changes have also been made to the first round of auditions where contestants have been able to perform with backing dancers and even their beloved pets such as cats and dogs. Explaining the revamped process, Cowell said: "We basically said to ourselves that we shouldn't apply any rules to the auditions. If they want dancers, this or that, dogs, cats – well, I don't care about cats – but you can do what you want. A couple of auditions I have sat there and thought how I have never seen anything like it on this show. They have really put the effort in; I think it's made the show better."

Fans of the popular series are keen to see how the new judges gel but the TV boss could not be happier with their chemistry, crediting singer Ora, 24, for reigniting Fernandez-Versini's interest in the show. He said of Ora: "She belongs with The X Factor! She's been a revelation. I was telling some friends the other day, she's got an incredible heart, she's funny, smart, interesting and really wants the contestants to do well.

"I said to her [Cheryl] the other night, 'You've got your mojo back'. She's really enjoying being on this show, it's not like a job, she's enjoying it and I think that's got a lot to do with Rita."

The X Factor returns on 29 August at 8pm on ITV.