Katy Perry's movie could prove a flop at the box office.

The 'Wide Awake' singer's 3D documentary, 'Katy Perry: Part Of Me', only brought in £4 million in the US on it's opening weekend, despite taking £7.7million to make.

Katy's fly-on-the-wall film has had a modest start compared to Justin Bieber's 'Never Say Never' which made £19 million in its opening weekend in 2011. Miley Cyrus' movie 'Hannah Montana: Best of Both Worlds Concert Tour' also grossed £20 million in 2008.

Paramount remains hopeful about the film's success, however. An executive told Deadline that the film would have ''much longer and better legs'' than Justin's film, which benefited from the teen singer's fanatical support base.

The concert movie documents the 27-year-old star's 'California Dreams' world tour, from her backstage antics to the breakdown of her marriage to comedian Russell Brand.

Katy split from Russell in December after 14 months of marriage and is now believed to be dating Florence + the Machine guitarist Robert Ackroyd, but she has said their relationship is not serious.

The film is being overlooked at the box office in favour of blockbuster 'The Amazing Spider-Man', which brought in a massive £90 million during its opening week.

Speaking about her film, Katy said: ''I wanted to show people this parade that surrounds me, I wanted them to see the engine. I wanted people to be able to experience the tour and all the joy it brought, which is why we shot it in 3D.''