Katy Perry the American singer took to the stage to perform her new single Fireworks, there was no missing her in a eye-wateringly tight sparkly catsuit.

In keeping with the song's title, the Lycra bodysuit was covered in glittery firework designs as she danced around to a backdrop of spectacular pyrotechnics.

What a cracker: Katy Perry performed her new single Firework in a sparkly catsuit on the X Factor results show

Leaving little to the imagination: Katy wrote of her 'excitement' about her outfit on her Twitter page before taking to the stage

It was somewhat of a return to the show for Ms Perry, who stepped in as a guest judge at the Dublin auditions last summer while Dannii Minogue was on maternity leave.

But as she came back to the show purely as a performer, she let Simon Cowell know she was interested in joining the judging panel when he starts up with U.S. version of The X Factor.

The 25-year-old said: 'I'm waiting for the call from Simon really.'

Belting it out: Katy showed off her contralto range in the uplifting song

Call health and safety: Katy was accompanied by 'human Catherine wheels' shooting pyrotechnic over the stage

Supportive: Katy's fiancé Russell Brand watched from backstage

As she chatted to host Dermot O'Leary after her performance, she admitted she found it just as nerve-wracking singing as she did at the judges' table.

She said: 'It's still nerve-wracking cos you're being judged. Did I do OK?'

Writing on her Twitter page after the show, she said: 'Oh my gawd, I was so nervous! Thanks X Factor for making me feel like I was actually one of the contestants.'

In contrast to some of the guest performers who often mime on the results show, Katy chose to sing the track live.

While she could be commended for singing live instead of using a backing track, it was clear to hear she struggled with some of the higher notes.

Reunion: Past contestant Diana Vickers also performed her new single My Wicked Heart on the show

Legal action: The pop star is in hot water with rock band The Red Hot Chili Peppers, who claims the chorus copies their 1992 hit Under the Bridge

Perry arrived in London on Friday to prepare for tonight's show and was soon joined in the British capital by fiancé Russell Brand.

The couple, who celebrated their one year anniversary as a couple last month, are expected to marry in India next weekend.

Among the celebrity guests expected to attend include Jonathan Ross, Noel Gallagher and David Walliams, with Rihanna being one of Perry's bridesmaids.

The rumoured wedding venue is the Taj Rambagh Palace in Jaipur, where the couple got engaged last New Year's Eve.

Relieved: Judges Cheryl Cole and Dannii Minogue head home after avoiding losing contestants last night

Russell accompanied his fiancée to the show and tweeted from backstage: 'At X-Factor. My favourite is Wagner- he looks like my dad plus he wrote all those great operas.'

Former X Factor contestant Diana Vickers also returned to the show to sing her new single My Wicked Heart. Dressed in a black and blue caped leotard, the pop star performed on a circus set with drummers and acrobats.

Like Perry, the 19-year-old admitted to nerves being back on the X Factor stage again, and said it 'was like school,' meeting the 'next class.'

Long weekend: Despite losing another act, Simon smiles as he exits the studios, while Dannii's partner Kris Smith carries baby Ethan to the car

While the new single was only released yesterday, Diana is already embroiled in legal action of the up-tempo track.

Executives at Warner/Chappell Music claim that the chorus blatantly copies their clients The Red Hot Chili Peppers' 1992 hit Under the Bridge.

There is an obvious resemblance between the two tracks, and Diana has even admitted to listening to the track before penning her own song.

She said in a recent interview: 'Yeah, that happened without even knowing.

High spirits: Katie looked thrilled to not be in the bottom three, while Cher stayed in costume

Heading home: Belle Amie escaped elimination after being saved by the judges, while One Direction's Liam and Rebecca both received positive feedback

'We wrote the song in an hour. We had the song and it didn't have the My Wicked Heart bit in it and then we put the vocal in and we were like, "Why does it sound so familiar?"

'Then we realised it was because we were listening to Under The Bridge the day before.

'We were saying, "Should we change it? Should we not? What should we do? Sod it, no, we're just going to keep it, it works".'

But perhaps Miss Vickers shouldn't have been so frank about her inspiration. A source told the Sun, 'She has done herself no favours by revealing she listened to the track while writing My Wicked Heart.'

No worries: Despite sounding off on this morning's Daybreak, rejects Storm Lee and Diva Fever looked in good spirits as they made a loud exit