Katy Perry has revealed that she had a hand in making Britney Spears' latest single.

The 'Toxic' star recently recorded the song 'Ooh La La' for the Smurfs 2 film, which Perry worked as a voice actor on.

Speaking to E! News at the movie's Los Angeles premiere, the pop songstress revealed that she actually laid down some backing vocals on the track alongside songwriter Bonnie McKee. She said:

"Me and Bonnie [McKee] secretly did some background vocals on that song. So maybe listen for our voices."

As previously reported, Katy Perry recently became the most followed female on Twitter, amassing over 39.9m followers.

However, she has some way to go to beat Justin Bieber, who is the most followed person on the social networking website with 42.2m fans.