The group also delivered a petition with 270,000 signatures to Google on Monday urging the group to quit.
Google reportedly considered leaving the chamber, but not for the reasons cited by SumOfUs.
Google disagreed with the Chamber's aggressive lobbying campaign in support of two copyright protection bills, the Stop Online Piracy Act and the Protect IP Act. The measures' supporters said the bills were necessary to curb online content theft, but Google and other Web companies argued they would impose unreasonable burdens on businesses and could stifle online innovation.
Lawmakers pulled the bills earlier this year after Google and thousands of other websites staged an online protest to draw attention to the issue.
Google and the Chamber of Commerce declined to comment.