Activists seeking greater transparency for online political ads say they've been struggling to monitor ads on Facebook after changes by the company.

Tools created by WhoTargetsMe and ProPublica, groups based in Britain and the US, respectively, have been limited by the social networks' crackdown on third-party plug-ins, The Guardian reported over the weekend.

The browser extensions have allowed the groups to gather data on political ads, with users' permission, to reveal advertising methods and figure out why campaigns target certain people.

WhoTargetsMe's software stopped working in recent weeks, group co-founder Sam Jeffers told The Guardian, and Facebook has allegedly made fixing the issue more challenging than in the past.

Facebook said the change came as a result of its limiting third-party plug-ins from accessing unauthorized data from the social network, even though WhoTargetsMe gets permission from its users.

"We regularly improve the ways we prevent unauthorized access by third parties like web browser plugins to keep people's information safe. This was a routine update and applied to ad blocking and ad scraping plugins, which can expose people's information to bad actors in ways they did not expect," Facebook spokesperson Beth Gautier said Monday in an emailed statement to CNET.

Last summer, Facebook created its own publicly viewable election ad database for the US and Brazil, showing all of a given advertiser's previous ads, the amount spent and the demographics the ads targeted. The company expanded the database to the UK in October, and it announced plans Monday to bring the service to the rest of the EU in late March, before the European parliamentary elections.

In an emailed statement, WhoTargetsMe's Jeffers said his group welcomed Facebook's new transparency measures, but that it also "seems like a backwards step."

"Facebook now admits it doesn't have all of the answers to the problems it has created, and welcomes outside input, yet they seem to be trying to stop a tiny citizen-led project with a track record of pointing out how things could be better," he wrote on Monday.

"We think WhoTargetsMe has added to the debate around the use of targeted ads and showed a way forward as to how society can respond. We're planning to do more of that work, despite Facebook's attempts to slow us down."

ProPublica confirmed via email that its own political ad transparency tool "has also been restricted by Facebook," noting that it plans to publish its own story on the matter.

First published Jan. 28, 7:01 a.m. PT.
Update, 8:56 a.m. PT: Adds WhoTargetsMe and ProPublica statements.

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