Facebook is to take the unprecedented step of building a notification tool enabling members to establish whether they inadvertently ‘liked’ pages that were in fact serving as Russian fake news sites.

The move will allow people to establish whether they were duped by ‘foreign actors’ during the US presidential election campaign following Facebook’s own estimates that as many as 126m Americans may have seen content written by Russian agents over the past two years.

Pages published by the Russian-backed Internet Research Agency have since been deleted but the new tool, launching next month, will give people the chance to go back in time and trace their interactions with the material.

Explaining its latest move in a blog post, Facebook wrote: “It is important that people understand how foreign actors tried to sow division and mistrust using Facebook before and after the 2016 US election.

"That's why, as we have discovered information, we have continually come forward to share it publicly and have provided it to congressional investigators. And it's also why we're building the tool we are announcing today."

Facebook has uncovered thousands of posts and paid advertisements linked to Russia, many of which sought to sow racial divisions and social discord.