LONDON — Google said on Wednesday that it would begin requiring more information from buyers of online ads linked to next year’s European Parliament elections, expanding a program introduced for political ads in the United States.

The company said in a blog post that people and groups buying ads that mention a political party, a candidate or an officeholder related to the parliamentary elections would need to make clear who is paying for the advertisement. The company will also require verification that they are citizens, legal residents or groups lawfully allowed to participate in the election.

Google and Facebook, the two largest online advertising platforms, are facing pressure to protect against the kind of foreign misinformation campaigns that were discovered in the 2016 presidential election in the United States. The companies operate advertising systems that are largely automated, making the networks immensely profitable but harder to police.

The European Parliament elections, in May, will be for 705 seats across 27 countries. The vote doesn’t often draw widespread attention, but the coming campaign is being closely watched as a wider referendum on the role of the European Union in the region. On one side is an emerging populist wing, represented by anti-immigration groups in Italy and Germany, that’s wary of the influence Brussels carries in the region. On the other side are supporters of a more united Europe, such as President Emmanuel Macron of France.