New legislation in the U.S. Senate that would allow Internet users to tell companies to stop tracking them is unnecessary and could slow e-commerce growth, some tech groups said.

Sens. John "Jay" Rockefeller, a West Virginia Democrat, and Richard Blumenthal, a Connecticut Democrat, reintroduced do-not-track legislation on Thursday. The Do-Not-Track Online Act, similar to legislation Rockefeller introduced in 2011, would require all online companies to honor do-not-track requests from consumers.

Online companies have failed to live up to promises to honor do-not-track requests, Rockefeller said in a statement.

"Online companies are collecting massive amounts of information, often without consumers' knowledge or consent," he added. "Consumers should be empowered to make their own decision about whether their information can be tracked and used online. My bill gives consumers the opportunity to simply say 'no thank you' to anyone and everyone collecting their online information."

But industry efforts to give consumers control over their data are working, countered Lou Mastria, managing director of the Digital Advertising Alliance, a trade group for online advertisers. The DAA's own program allowing consumers to opt out of online tracking covers more than 90 percent of the online advertising market, he said.

The DAA's opt-out mechanism and online advertising principles are based on U.S. Federal Trade Commission recommendations, he said. Ads with the DAA's icon are served online a trillion times a month, he added.

DAA launched the self-regulatory program in 2010 and announced its first 100 participating companies in mid-2011, shortly after Rockefeller introduced his earlier do-not-track bill.

"A lot has changed since the last time the senator put the bill out," Mastria said. "We brought [do-not-track notices] to reality at Web-wide scale."

Legislation isn't needed because self-regulation is working in the U.S., he added. "The reality is we've stepped up and delivered at every turn," he said.

The do-not-track bill would harm Internet companies that depend on tracking to deliver targeted advertising, added the Information Technology and Innovation Foundation, a tech-focused think tank. The bill would hurt consumers because so much Web content is supported by targeted advertising, the foundation said.

"The success of the Internet is rooted in the availability of access to free, ad-supported online content and services," Daniel Castro, a senior analyst at ITIF, said in an email. "Given the importance of the Internet to the U.S. economy it is unfortunate to see legislation introduced that will discourage growth in this important sector."

In addition to giving Web users a do-not-track option, the new bill would allow the FTC to pursue enforcement action against any company that does not honor consumer opt-out requests, and it would require companies to collect only the information they need to effectively deliver their website or online service. The bill would require online companies to destroy or anonymize personal information they no longer need.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is grant_gross@idg.com.