Some of the original engineers of the Internet called Thursday for lawmakers to scrap anti-piracy bills, saying the proposals would pose major technological barriers for the Web and stifle new innovations.

The letter comes as House Judiciary committee members on Thursday debate the Stop Online Piracy Act introduced by Lamar Smith (R-Tex.) that has drawn impassioned support from media firms but opposition by Web firms and some public interest groups.

At the hearing, California Reps. Zoe Lofgren (D) and Darrell Issa (R) have asked the committee to reconsider the bill and amendments to it in a hearing.

But many lawmakers of both parties are in support of the legislation.

“Because the U.S. produces the most intellectual property, our nation has the most to lose if we fail to address the problem of rogue sites,” said Judiciary Committee Chairman Smith said in a statement.

Ranking member John Conyers (D-Mich.) said the bill should be passed to protect jobs.

“Online property crime robs American artists and harms American consumers,” Conyers said.

Engineers, however, have warned that the bills have been introduced without enough consideration of how laws would affect the Internet.

Vint Cerf of Google, domain name system software author Paul Vixie and Internet routing engineer Tony Li were among 83 high-profile engineers who signed an open letter to Congress in opposition to the House Stop Online Privacy Act and Senate Protect Intellectual Property Act.

“If enacted, either of these bills will create an environment of tremendous fear and uncertainty for technological innovation, and seriously harm the credibility of the United States in its role as a steward of key Internet infrastructure,” the engineers wrote.

Most concerning are proposals in both bills for law enforcement to take down sites that are dedicated to the illegal trade of copyrighted material. By striking down domain names, the legislative proposals would fragment the Internet’s global domain system, they say.

They also fear the bills would lead to censorship and put undue burden on Web sites.

Here’s the letter:

We, the undersigned, have played various parts in building a network called the Internet. We wrote and debugged the software; we defined the standards and protocols that talk over that network. Many of us invented parts of it. We're just a little proud of the social and economic benefits that our project, the Internet, has brought with it.

Last year, many of us wrote to you and your colleagues to warn about the proposed "COICA" copyright and censorship legislation. Today, we are writing again to reiterate our concerns about the SOPA and PIPA derivatives of last year's bill, that are under consideration in the House and Senate. In many respects, these proposals are worse than the one we were alarmed to read last year.

If enacted, either of these bills will create an environment of tremendous fear and uncertainty for technological innovation, and seriously harm the credibility of the United States in its role as a steward of key Internet infrastructure. Regardless of recent amendments to SOPA, both bills will risk fragmenting the Internet's global domain name system (DNS) and have other capricious technical consequences. In exchange for this, such legislation would engender censorship that will simultaneously be circumvented by deliberate infringers while hampering innocent parties' right and ability to communicate and express themselves online.

All censorship schemes impact speech beyond the category they were intended to restrict, but these bills are particularly egregious in that regard because they cause entire domains to vanish from the Web, not just infringing pages or files. Worse, an incredible range of useful, law-abiding sites can be blacklisted under these proposals. In fact, it seems that this has already begun to happen under the nascent DHS/ICE seizures program.

Censorship of Internet infrastructure will inevitably cause network errors and security problems. This is true in China, Iran and other countries that censor the network today; it will be just as true of American censorship. It is also true regardless of whether censorship is implemented via the DNS, proxies, firewalls, or any other method. Types of network errors and insecurity that we wrestle with today will become more widespread, and will affect sites other than those blacklisted by the American government.

The current bills — SOPA explicitly and PIPA implicitly — also threaten engineers who build Internet systems or offer services that are not readily and automatically compliant with censorship actions by the U.S. government. When we designed the Internet the first time, our priorities were reliability, robustness and minimizing central points of failure or control. We are alarmed that Congress is so close to mandating censorship-compliance as a design requirement for new Internet innovations. This can only damage the security of the network, and give authoritarian governments more power over what their citizens can read and publish.

The US government has regularly claimed that it supports a free and open Internet, both domestically and abroad. We cannot have a free and open Internet unless its naming and routing systems sit above the political concerns and objectives of any one government or industry. To date, the leading role the US has played in this infrastructure has been fairly uncontroversial because America is seen as a trustworthy arbiter and a neutral bastion of free expression. If the US begins to use its central position in the network for censorship that advances its political and economic agenda, the consequences will be far-reaching and destructive.

Senators, Congressmen, we believe the Internet is too important and too valuable to be endangered in this way, and implore you to put these bills aside.