Mozilla has sent a letter to the European Commission to raise concerns about the lack of publicly available data about political advertising on Facebook, urging the EU body to present the issue to Facebook.

The browser developer is in the process of developing a ‘Firefox Election package’ for the EU’s upcoming parliamentary elections, but Facebook’s browser add-on policies mean that Mozilla cannot deliver the transparency it wishes with the package. In particular, Mozilla takes issue with the fact that Facebook’s Ad Archive API isn’t publicly available.

Mozilla hopes to include ‘two key features’ in its Ad Analysis for Facebook ad-on. The first would analyse a user’s Facebook feed and identify what ads the user is seeing and identify how the user is being targeted. The second would compare this information to publicly available data sources to see how the ads seen by users may differ to the ads seen by others.

“Transparency cannot just be on the terms with which the world’s largest, most powerful tech companies are most comfortable,” said Denlle Dixon, Mozilla COO, in a letter to Mariya Gabriel, commissioner for digital economy and society. “To have true transparency in this space, the Ad Archive API needs to be publicly available to everyone.”