The internet giants are objecting to a clause in the Digital Economy Bill, which had its second reading in parliament yesterday. The clause would allow the secretary of state for business to introduce new laws regarding copyright.
The government has said the purpose of giving such powers to the business secretary was to help copyright legislation keep up with changing technologies, but the move has sparked fears that it will hand over unprecedented levels of power to one individual.
In the letter, the companies say that while they support the principle of protecting copyright owners, it says that clause 17 "opens the way for arbitrary measures. This power could be used, for example, to introduce additional technical measures or increase monitoring of user data even where no illegal practice has taken place".
The companies say that they fear such a move could discourage innovation and impose unnecessary costs on industry.
Broadband providers have already outlined their objections to another section of the Digital Economy Bill, which will mean that people who repeatedly download copyrighted materials without paying for them are cut off from broadband internet access.
Members of the public are being urged by high profile Twitterers, including Stephen Fry and sitcom writer Graham Linehan, to sign a petition objecting to the law.