Google gets a "D" in digital rights -- and it's the best-performing Internet or telecommunications company in a study on freedom of expression and privacy released on Tuesday.

The inaugural Ranking Digital Rights Corporate Accountability Index looked at privacy, freedom of expression and commitment to those policies at eight publicly listed Internet and eight publicly listed telecomunications companies around the world. Researchers scored companies using peer reviews, company feedback and quality control.

"There are no 'winners,' " the report says. "Even companies in the lead are falling short. Across the board, companies need to improve their commitments to, and disclosures of, policies and practices that affect users' freedom of expression and privacy."

Google led the Internet category, with an overall score of 65 percent out of 100. Its best category was commitment, where it scored a 78 percent. Google's weakest category was privacy. Yahoo, Microsoft and Twitter all had scores in the 50s, while Facebook scored 41. Russian Internet provider had the lowest score among Internet companies, with a 13 percent.

Britain-based Vodafone was the highest scoring telecommunications company, followed by AT&T. Vodafone's strongest showing was in the commitment category. Etisalat, based in the United Arab Emirates, got the lowest score.

Companies aren't successfully telling users about what information is collected about them, how it's used, shared or retained, according to the report.

"This lack of clarity means that users, and especially at-risk users such as journalists, activists, or anyone living under a repressive regime, are not fully aware of who can access what specific information the company holds about them," it says.

How free is your expression on those sites and services? It's hard to say, according to the report. None of the companies share information about the volume and types of content they delete or block while enforcing the terms of service. Companies argued that disclosing this type of information would be "infeasible and counterproductive," according to the report.

That approach pleases regulators at the expense of users, the group wrote.

Most companies don't have readily displayed processes for receiving and addressing grievances. Others lack end-to-end encryption. Messaging service Kakao of South Korea scored well in these categories, while Bharti Airtel of India was the highest scoring telecommunications company for remedies.

But it's not all bad news.

"Every company does something well," the report says. Freedom of expression and privacy are valued around the world, according to the report, with "transparency reporting" about government and private requests becoming a more popular practice. However, those reports on third-party requests range in clarity, quality and comprehensiveness.