Google, Yahoo, eBay, Facebook, Orange, Talk Talk and BT have singed an open letter to the Financial Times condemning a bill in parliament that they say "threatens freedom of speech and the open internet".
The Digital Economy Bill has all party support in Westminster, but it is opposed by many of the largest internet, telecom and e-commerce companies in the UK who are determined to stop legislation to force internet providers to block sites carrying pirated music and films.
The companies are backed by Stephen Fry, Labour MP Tom Watson, the former minister for digital engagement, campaign groups and academics/ They argue that the bill, if it becomes law, would not tackle copyright infringement as intended. Instead it would undermine the government's objectives for promoting Britain's digital economy.
"A policy that would encourage the blocking of websites by UK broadband providers or other internet companies is a very serious step for the UK to take," according to the signatories. "There are myriad legal, technical and practical issues to reconcile before this can be considered a proportionate and necessary public policy option."
The BPI, which represents record labels and has campaigned for stronger online copyright protection, told the Financial Times the internet companies' concerns were "pure scaremongering".
The House of Lords will vote on the bill next week before passing it back to the House of Commons.