MOSCOW   -   House speaker Nancy Pelosi has strongly criticised Facebook for failing to tackle misinformation after the social media network refused to take down a video that had been doctored to make her appear drunk or ill.

Pelosi, the highest ranking woman in Congress, is the most senior US politician to have accused Facebook of “wittingly” allowing the spread of misinformation promoted by Russia during the 2016 US election.

“We have said all along, poor Facebook, they were unwittingly exploited by the Russians,” Pelosi said in an interview with California radio station KQED on Wednesday. “I think wittingly, because right now they are putting up something that they know is false. I think it’s wrong. I can take it. But [Facebook is] lying to the public.”

She added: “I think they have proven – by not taking down something they know is false – that they were willing enablers of the Russian interference in our election.” Facebook did not immediately respond to a request for comment from KQED.

Last week, Facebook said it would continue to host the video of Pelosi that has been edited and slowed down to give the impression that she was slurring. Several versions of the clip appeared to be circulating.

Donald Trump’s personal lawyer and the former mayor of New York, Rudy Giuliani, was among the Trump supporters who promoted the story. He tweeted – then deleted – a link to a copy of the video on Facebook with the caption: “What is wrong with Nancy Pelosi? Her speech pattern is bizarre.”

The viral success of the crudely produced video highlights the challenges in fighting online disinformation when individuals are willing to share material that backs their own political views, even when it is accompanied by warnings.

Despite the apparently malicious intent of the video’s creator, Facebook said it would only downgrade its visibility in users’ news feeds and attach a link to a third-party factchecking site pointing out that the clip is misleading. Facebook only took the action following inquiries from the Washington Post, which first reported the story.

Donald Trump last week tweeted a different altered video of Pelosi, which aired on Fox Business network, and had been heavily edited to make it appear as if she was stuttering and slurring her language. The president captioned the tweet: “PELOSI STAMMERS THROUGH NEWS CONFERENCE”.