"But unfortunately, Senate Leader Harry Reid [(D-Nev.)] is pushing forward with legislation that is deeply flawed and still needs much work," he said.
Blunt was elected vice chairman of the Republican conference last month.
“I continue to believe that we can come to a solution that will cut off the revenue sources for foreign websites dedicated to counterfeiting and piracy that steal American jobs, hurt the economy, and harm consumers," Blunt said. "But the Protect IP Act is flawed as it stands today, and I cannot support it moving forward.”
Sen. Marco Rubio (R-Fla.) also dropped his co-sponsorship of the legislation on Wednesday.
The Protect IP Act and its House counterpart, the Stop Online Piracy Act (SOPA), are designed to go after foreign websites that offer illegal copies of movies, songs and TV shows with impunity. The bills would empower the Justice Department and copyright holders to demand that search engines delete links to sites deemed to be “dedicated” to copyright infringement. Ad networks and payment processors would be prohibited from doing business with the sites.
Movie studios, record labels and business groups say legislation is needed to curb online copyright infringement, which is hurting businesses and eliminating jobs.
But on Wednesday, thousands of websites, including Wikipedia, Google and Reddit, staged a massive protest against the legislation.
The English version of Wikipedia shut down entirely, redirecting users to a page criticizing the legislation.
Google, the most visited site in the world, placed a black box over its logo. Users who click on the box are sent to a petition claiming the bills would "censor the Web and impose harmful regulations on American businesses."
The Senate is expected to vote on the legislation on Tuesday.