The pair were announced for the show after months of speculation, replacing departing judges Nicole Scherzinger and Paula Abdul.

However, speaking to E! News, vocal star John Legend criticised the show for having Britney Spears and Demi Lovato judge the talent when they "aren't really singers" themselves. He said:

"You know, it's interesting. It should be very interesting. I don't have much to say. It's interesting when people you know who are judging singing competitions when they aren't really singers. It's interesting."

Speaking to BBC Radio 4, Cowell said that he thought to truly live up to the show's ethos of putting the voice first then it might have been better off on the radio.

As such, he feels that as the contestant's identities were revealed, the programme has turned into an X Factor rip off, with "dancers, graphics and lights" behind the performances. He said:

"That show puzzles me because it starts off and 'it's all about the voice'. So my first thought is, 'Why isn't this on radio?' because what's the point in looking at them. Then suddenly I'm watching it a week or two weeks ago and it's the same as The X Factor. They've got dancers behind them, graphics, lights. Same show."

A smug Cowell concluded: "When The Voice came along it was like, 'Roll your sleeves up, we're in for a bit of a punch-up'. I'm smiling now."

Recently, the 'Hero' sensation told U.S. show Extra that she wasn't interested in the televised talent show and admitted that she didn't care who had signed up as judges:

"You think I focus on that stuff? Have we met? I love (Spears), honestly. I think she's a very nice person, but I don't care who's going on that show - as long as it's not me."

Earlier today (May 16), Carey tweeted a public message to both Simon Cowell and new panelist Britney Spears to clear up the speculation, writing:

"@BritneySpears & @SimonCowell of course I luv+care about you dahhlings, congrats! U never know what's true or gossip, I was joking around! xo"

As previously reported, X Factor USA ended months of speculation on Monday (May 14) after they confirmed that Spears and Lovato would be taking up the two vacant seats on the show's judging panel.

Speaking to Extra, Simon Cowell revealed that it wasn't literally until the day of the announcement that he was sure the pair were going to sign the dotted line. He said:

"Right up until today, I wasn't 100 percent sure it was going to happen or not. Because when you're negotiating with people like that who are big stars, you don't just sign the contract overnight. There's stuff you've got to sort out."

Cowell also opened up on the negotiations between himself and Britney Spears' manager, suggesting that her party were quick to rush into a deal. He said:

"I remember her manager, Larry, saying, 'Britney wants to speak to you' and about a week had passed and she got on the phone and said 'Simon, I want to tell you I'm in, and we have a deal.' [Her manager] said, 'We haven't quite got a deal yet!'... She spoke too soon."

Spears, who was officially confirmed as a new judge on X Factor USA last night (May 14), will not make a cameo on the popular musical drama this time around but instead the episode will feature 8 of her hits.

EW.com reports that the episode will be second in the show's impending fourth season and it is set to premiere this coming autumn.

Back in 2010, the 'Hit Me Baby (One More Time)' superstar appeared as herself on the 'Britney/Brittany' episode of 'Glee' and she lent 5 of her iconic singles to the talented cast for the show.  

Following the exciting confirmation of Spears' new talent show judging role, she opened up about being chosen for the job and told the press:

"I'm so excited about this whole experience. It's going to be so much fun and so different from anything I've ever done. I'm ready to find a true star."

After months of rumour and speculation, Spears and Lovato were announced yesterday (May 14) as the TV talent show's two new judges.

Speaking at a press conference to mark the announcement, Spears said that she is "so excited" about the job and is raring to go. She said:

"I'm so excited about this whole experience. It's going to be so much fun and so different from anything I've ever done. I'm ready to find a true star."

Demi Lovato meanwhile echoed Spears' sentiments, adding that she is hoping to "represent her generation" on the show. She said:

"I am totally stoked to be here. I'm excited to represent my generation and I'm ready to find the winner."

The rumour mill has been in overdrive for weeks after previous judges Nicole Scherzinger and Paula Abdul vacated their seats.

X Factor supremo Simon Cowell had previously been coy on rumours that Britney Spears would land a role on the show, but today (May 14) the show confirmed on Twitter that Spears will be joined by Demi Lovato as X Factor USA's new judges.

Spears meanwhile took to Twitter to post a photo of all four judges together, sporting the hashtag:

"#SimonBritneyDemiLA."

The US hip-hop star, who plays London’s 02 Arena with Jay-Z later this week, told the Daily Star Sunday that he believes Cole doesn’t need former X-Factor boss Simon Cowell to become an international success.

He said: “I don’t see Cheryl ever working with Simon again. 

“She has gone on to big things since the US X Factor. She is taking over the world in music and in movies.”

The 34-year-old, who is preparing to release his upcoming G.O.O.D. Music compilation album, went onto add: “There’s no looking back for her, just forward. She’s going to get bigger and bigger.”

17-year-old Ashleigh and her talented dog Pudsey, both from Northampton, have walked away with the incredible £500,000 prize and took the stage for a final time to perform their heartwarming routine.

Only Boys Allowed came in third place and opera singers Jonathan and Charlotte were named runners up of this year's competition. Speaking to Ant and Dec after she was crowned the winner, Ashleigh explained that she was completely overwhelmed by the support from the public:

"I just want to say a massive thank you to everyone who voted and I'm so proud of Pudsey."

Music mogul Simon Cowell was visibly pleased that a dancing dog act had finally won Britain's Got Talent and said: "This has been my favourite year."

The 27-year-old, who was speaking at the launch of the Radio1 and 1Xtra Academy earlier this week, told the Daily Record that she has taken her fellow talent show stars under her wing:

“They’re having a lot of fun. I give them a little bit of advice sometimes. I tell them to enjoy it.”

However, the ‘Bleeding Love’ star ruled out any romantic involvement following Liam Payne’s admission that he had a crush on her, adding: “He’s sweet. But they’re, like, two.”

The 2006 X-Factor winner, who recently expressed her fears over the rise of young gangs, also stated that her relationship with Simon Cowell has always been strictly platonic following revelations about his private life in Tom Bower’s recent biography.

She said: “He was never flirty with me at all. He was more like an uncle.”