Cowell was joined by Working Title co-chair Tim Bevan and United 93 director Paul Greengrass.
In a letter to the Members of Parliament, they asked the government to support the digital economy bill. Author Terry Pratchett and Spooks creator Stephen Garrett also signed the letter.
If the Labour government loses in the coming general election, the digital economy bill may not get passed. Internet service providers such as Virgin Media and Carphone Warehouse are reluctant to cut off their subscribers.