Supermodel Kate Moss has taken a swipe at Sienna Miller - branding her an "amateur".The catwalk queen is reportedly sick of film star Sienna winning modelling assignments and thinks the blonde beauty should stick to acting.Moss is said to be furious Sienna is featuring on magazine covers she thinks should be hers.The 32-year-old model lashed out at Sienna while she enjoyed a boozy night out at the Ritz in Paris.A source told Britain's The Sun newspaper: "She was loudly saying Sienna was not a professional model and she should be getting front covers - not an actress."Sienna is a real threat because she is younger - and has kept her nose clean. But Kate is not ready to give up her throne."Another insider added to Britain's Daily Mirror newspaper: "She also said how she thought Sienna's stab at celebrity has failed. Kate said, 'Sienna has blown it now - she's had her last chance. But she was never one of us anyhow'."