Google said on Monday it had removed ads for companies that charge people large fees to register to vote or harvest their data, which appeared when users searched for voter information.
A Google spokeswoman told Reuters that the company's misrepresentation policy barred such ads, which were found by the nonprofit watchdog Tech Transparency Project when searching for terms such as "register to vote," "vote by mail," and "where is my polling place."
As in all major democracies, voters in the United States do not have to pay to register to vote.
Tech Transparency Project said in a report on Monday that nearly a third of the more than 600 ads generated by its Google searches took users to sites that try to charge large fees for voter registration services, extract personal data for marketing purposes, install deceptive browser extensions, or serve other misleading ads.
The report said that the first ad in a Google search for "register to vote" directed users to a site from PrivacyWall.org that charged $129 for "same-day processing" of voter registration.
PrivacyWall's CEO Jonathan Wu said in an email to Reuters that its service makes it easier for voters to register online without giving more data than is required, and that it does not share data for any purpose other than voter registration.
"Our goal is to create choice where none may exist. In order to make this possible, we charge consumers a fee which is clearly disclosed," said Wu, adding that the fee covered mail, staffing and other costs. "We will not let Google arbitrarily thwart our efforts to protect consumer privacy and to increase voter turnout."
A Google spokeswoman said the company did not yet know how the ads had got through its approval process, which uses a combination of automated and manual review.
"We have strict policies in place to protect users from false information about voting procedures, and when we find ads that violate our policies and present harm to users, we remove them and block advertisers from running similar ads in the future," the spokeswoman said.
The TTP report said: "Some people may find it difficult to distinguish Google ads from other kinds of content because as of January, search ads on Google feature the same type face and color scheme as organic search results."
Social media companies and online platforms, including Facebook and Twitter, are under pressure to curb misinformation on their sites in the run-up to the US presidential election in November.