Executives from BT, Virgin Media, Orange, Google, Talk Talk, Facebook and Consumer Focus have written to the Financial Times outlining their grave objections to the proposed law and their view that while the law's aim may be laudable, it "would have unintended consequences that far outweigh any benefits it could bring".
A proposal from Conservative peer Lord Howard of Rising and Liberal Democrat peer Lord Clement Jones proposed amending the Digital Economy Bill. That change replaced ministers' much-opposed powers to amend copyright legislation without full Parliamentary scrutiny with court powers to force ISPs to block access to websites accused of hosting copyright-infringing material.
The House of Lords voted to accept the amendment to the Bill, which will be the subject of one more Lords debate before passing to the House of Commons.
"This amendment not only significantly changes the injunctions procedure in the UK but will lead to an increase in internet service providers blocking websites accused of illegally hosting copyrighted material without cases even reaching a judge," said the letter to the Financial Times.
Signatories to the letter also included actor and comedian Stephen Fry, the UK head of Yahoo!, the director of digital rights body Open Rights Group and the UK head of eBay.
"Endorsing 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," it said. "There are myriad legal, technical and practical issues to reconcile before this can be considered a proportionate and necessary public policy option."
The opponents of the amendment said that the Lords had not properly considered the implications of the amendment.
"The Lords have been thoughtful in their consideration of the bill to date. It is therefore bitterly disappointing that the House has allowed an amendment with obvious shortcomings to proceed without challenging its proponents to consider and address the full consequences. Put simply, blocking access as envisaged by this clause would both widely disrupt the internet in the UK and elsewhere and threaten freedom of speech and the open internet, without reducing copyright infringement as intended," it said.
"To rush through such a controversial proposal at the tail end of a parliament, without any kind of consultation with consumers or industry, is very poor lawmaking," said the letter.
The Digital Economy Bill's measures aimed at reducing online copyright infringement have been controversial since the publishing of the Bill last year. Despite the Digital Britain Report failing to recommend the disconnection of internet access used by people accused of file sharing, the Bill included just such a provision.
That has prompted opponents to claim that disconnections will be unfairly carried out on the basis of allegations rather than evidence and that they will punish other users of an internet connection who had not infringed any copyright.
The Joint Committee on Human Rights said last month that the Bill was too vague and that it could not assess whether or not the measures to be taken were compatible with the Human Rights Act without more detail.