The U.K.’s Institute of Practitioners in Advertising called for a moratorium on political microtargeting, deeming it “weaponized ad technology.” That’s the practice whereby brands and advertisers can select who gets a Facebook ad based on specific data including location, interests and even political opinions. Now, in the U.S. and Europe, advertising executives, researchers and government officials are scrutinizing the practice, saying it can be used to manipulate voters and polarize the electorate.

The New York Times reports that, also in the U.K., a July report from the Information Commissioner’s Office on political campaigns suggested an “ethical pause” on “the use of personal information in political microtargeting so that regulators and companies could consider the technology’s implications.”

“These techniques raise fundamental questions about the relationship between privacy and democracy, as concerns about voter surveillance could lead to disengagement with the political process,” wrote the British information commissioner Elizabeth Denham. A British Parliament report criticized “relentless targeting of hyper-partisan views, which play to the fears and prejudices of people, in order to influence their voting plans and their behavior,” and also “called for curbs on some microtargeting.”

Facebook, Google and Twitter all offer so-called data-mining services, “but Facebook’s gargantuan reach, vast holdings of user data and easy-to-use self-service advertising system have made it a lightning rod for political microtargeting.” The Cambridge Analytica scandal and investigation into how Russians interfered in the last U.S. presidential election has prompted the focus on microtargeting, which “was a central tool for foreign groups trying to interfere in elections.”

University of Wisconsin-Madison professor Young Mie Kim reported how the Kremlin-linked Internet Research Agency “used Facebook’s ad system to identify nonwhite voters” and then “tried to discourage those people from voting.”

“Russian groups appeared to identify and target nonwhite voters months before the election with benign messages promoting racial identity,” said Kim. “These groups later appeared to interfere in the elections with voter suppression messages.”

Based on criticism from investigative news organization ProPublica, Facebook has since “removed almost one third of the ad-targeting categories used by the Russian voter interference group [and] … removed the option for advertisers to exclude users in certain sensitive categories — like race, ethnicity, sexual orientation and religion – from seeing ads.” Still, advertisers (and bad actors) can target ads by the user’s “ZIP code, education level, brand of smartphone, and whether they are politically moderate, very conservative or very liberal.”

Not everyone is satisfied with these efforts, however, as “some civil rights experts and researchers, say that Facebook’s recent efforts have done little to disable microtargeting as an engine of voter manipulation.” The Honest Ads Act, introduced in the Senate and still in committee, “would require online services to provide descriptions of each audience targeted by a political ad.”