Katy Perry is writing a song attacking Lily Allen.

The 'I Kissed A Girl' star - who was embroiled in a war of words with the 'Fear' singer earlier this year - has promised to "get nasty" when penning tracks for her new album and air opinions she has previously kept suppressed, sparking speculation it will include her feud with the British artist.

She said: "It's just going to be completely packed with what you want to hear about what I think. Everyone asks me, 'What do you think about this? What do you think about that? And about this person?' I don't really comment about that in public but I take it to the pen and I get nasty."

Katy says the record will be more grown up than her debut album, but promises her fans will still be able to relate to her music.

She added to BBC Newsbeat: "I'm looking to make a record that's more honest and it's going to be different.

"I'm not trying to alienate my fans necessarily but 'One of the Boys' was written from 17 to 23 and now I'm 24 so my perspective on life has changed.

"I'm not looking to make a record about, 'Hey, I got famous this year and you didn't... blah blah blah. This relates nothing to you.'

"It might be emotional but I don't think it's going to be sad emotional."