Facebook Inc. (FB) and Alphabet Inc.’s Google (GOOG) got slammed by Martin Sorrell, the CEO of advertising company WPP Group, who argued the social media giants have to control where the advertisements are placed as well as clamp down on fake news that shows up in their feeds and online.

In an interview with CNBC on the sidelines of the China Development Forum, Sorrell said Facebook and Google have “always maintained they were sort of digital engineers standing there with their digital spanners, trying to tighten the nuts on their digital pipes and not being responsible for the content that was going through the pipes," and as a result are not doing enough to combat fake news and where ads show up. "They can't just say look we're a technology company, we have nothing to do with the content that is appearing on our digital pages," Sorrell told CNBC.

Google, Facebook Could Lose Advertisers

But it’s not just the information that shows up on social media that’s getting Sorrell upset. He said Google and Facebook need to be held to the same standards when it comes to placing advertisements that traditional media have to adhere to. He pointed to the fact sometime ads are automatically placed next to questionable or inappropriate content even though Facebook and Google can control where the ads go.

"The big issue for Google and Facebook is whether they are going to have human editing at this point ... of course they have the profitability. They have the margins to enable them to do it. And this is going to be the big issue—how far are they prepared to go?" Sorrell said, noting more needs to be done to address those concerns. The executive warned that Facebook and Google could lose ad revenue if they continue to do nothing. Last week several prominent businesses and clients for Google’s advertising solutions pulled ads off its site when the company could not reassure them that their ads would not be placed against content that was inappropriate. Google has responded by revamping its advertising policies. (See also: Google to Revamp Policies After Clients Pull Ads.)

While Facebook and Google have gotten slammed in recent months over critics who contend they peddle fake news, favor liberal content over conservative news and don’t do enough to clamp down on all of it, both are taking steps to improve things. Facebook, for its part, has announced a slew of initiatives aimed at enhancing its reputation and cleaning the site of fake news. The most recent actions was taken earlier this month when it rolled out a system that allows users to tag alleged fake news as “disputed.” Facebook is relying on nonpartisan third parties to determine if a story flagged by a user is fake or factual. Stories that are tagged as disputed will also include links to websites that specialize in debunking conspiracy theories, alternative facts and fake news.