Google is scrambling to respond to criticism of its advertising policies after a wave of British media outlets—including The Guardian and the BBC—pulled their business from both Google and YouTube because their ads were appearing next to offensive content.
The Guardian was one of the first to announce on Thursday that it was withdrawing all of its advertising from Google and YouTube after ads promoting its membership program appeared next to “extremist material,” including YouTube videos of American white nationalists, a hate preacher banned in the UK, and a controversial Islamist preacher.
The advertising issue appears to be related to the use of AdX, Google’s DoubleClick Ad Exchange Service, which uses “programmatic” or automated trading of ads on various sites. This kind of trading places ads using a variety of algorithms, a process in which humans are rarely involved directly.
Guardian CEO David Pemsel said in a letter to Google that many brands feel they have to place their ads on the company’s services because of the dominant position that Google, YouTube and the DoubleClick ad platform have in the marketplace.”
“It is therefore vital that Google, DoubleClick and YouTube uphold the highest standards in terms of openness, transparency, and measures to avoid advertising fraud and misplacement in the future,” Pemsel said. “It is very clear that this is not the case at the moment.”
Get Data Sheet, Fortune’s technology newsletter.
The Guardian‘s move was quickly followed by the BBC, Channel 4, and a number of government departments, all of which stopped advertising with Google and its video service.
A U.K. government spokesman told the Guardian that the government had put a hold on any advertising with Google or YouTube, and that a Google representative had been “summoned for discussions” to explain the situation and its proposed remedy.
Last month, an investigation by The Times newspaper in Britain found that ads from dozens of major firms and various arms of the British government were appearing next to ISIS videos and other offensive content.
Facebook to Flag Fake News With a ‘Disputed’ Tag
A senior Google executive in the U.K. acknowledged the controversy in a blog post on Friday, saying the company does its best to ensure that client ads aren’t published alongside offensive content. “However, with millions of sites in our network and 400 hours of video uploaded to YouTube every minute, we recognize that we don’t always get it right,” he said.
Ronan Harris admitted that Google needs to “do a better job of addressing the small number of inappropriately monetized videos and content,” and that the company plans to introduce more ways for customers to control how and where their ads appear.
The news website Marketing Land, which has reported similar incidents with Google advertising in the past, said that “the rise of programmatic ad buying has created an environment in which reach and expediency have come at the cost of brand safety.”
Sir Martin Sorrell, the head of global ad agency WPP, told news site Business Insider that the advertising controversy reinforces his point that Google and Facebook and other platforms have to admit that they are media companies and face up to their responsibilities.
“We have always said Google, Facebook and others are media companies and have the same responsibilities as any other media company,” Sorrell said. “They cannot masquerade as technology companies, particularly when they place advertisements. GroupM… is talking to the digital media owners at the highest levels to encourage them to find answers to these brand safety issues.”