Six conservative U.S. senators voiced concerns Friday over the substance and procedural context of controversial legislation to block Internet piracy, noting potential economic damages and free speech restrictions the legislation might impose.

Sens. Chuck Grassley (R-IA), John Cornyn (R-TX), Orrin Hatch (R-UT), Jeff Sessions (R-AL), Mike Lee (R-UT), and Tom Coburn (R-OK), sent a letter to Senate Majority Leader Harry Reid (D-NV) on Friday expressing their concerns.

The letter, whose signatories include the ranking Republicans on the Budget, Finance, and Judiciary Committees, warns of “breaches in cybersecurity, damaging the integrity of the Internet, costly and burdensome litigation, and dilution of First Amendment rights” could result from passage of the hotly-contested PROTECT IP Act.

The legislation would empower the Justice Department to pursue legal action against any site that hosts content that violates intellectual property laws through measures that could include blocking access to such sites for all American Internet users. Given the concerns voiced by third parties opposed to the legislation, the letter states, Senate leaders “need to resolve as many outstanding concerns as possible prior to proceeding to floor consideration.”

The senators also reaffirmed their request that “the bill be fully debated and amendments not limited” when it does comes to the Senate floor – on Jan. 24, according to the current Senate schedule. That tight time frame, the senators warned, may not permit the substantive changes to the legislation needed to secure their support.

Here is the letter in full: