Cans of Dove deodorant, made by Unilever. The company's chief marketing officer says the crucial issue for digital advertisers is whether consumers trust what they see online © Bloomberg

US tech groups already face fierce scrutiny of their impact on society, from politicians and consumer advocates, activist investors and their own former employees. Now some of their biggest customers are stepping up criticism of a digital ad market dominated by Google and Facebook. Unilever, one of the world’s largest marketing spenders, is threatening to pull its ads from digital platforms if they “create division”, foster hate or fail to protect children.

It is not the first time Keith Weed, Unilever’s chief marketing officer, has criticised what he calls the “murky” world of digital media. In the past, he focused on the tech platforms’ lack of transparency over data and metrics, pressing them to make sure ads were being viewed by real people. The crucial issue now, he argues, is whether consumers trust what they see online, given concerns about fake news, election meddling, trolling and the platforms’ failures to police content that glorifies terrorism or exploits children.

These are generally seen as ethical issues demanding a response in the form of regulation, such as Germany’s introduction of fines for companies that fail to remove hate speech or fake news. But from the advertisers’ point of view, it is a matter of quality control: the digital platforms promise that ads will appear next to appropriate content, and they have proved unable to ensure that this is always the case.

The tech groups are stepping up their efforts to police content, in response to growing public concern and the threat of regulation. However, they have in general been reluctant to accept responsibility or to take action that would entail any significant change to their business model. It is reasonably clear that they could do more, if it became a commercial imperative.

YouTube’s experience last year illustrates this. The video site took a hit to its bottom line when big customers quit after ads appeared next to extremist content and videos featuring children and explicit comments. YouTube is now hiring more people to review where ads run and take down unacceptable content. But it has been more hesitant about rule changes that could anger its creator community.

However, YouTube is trying to fix a relatively clear-cut problem. Advertisers are voicing a much broader concern: that consumers increasingly dislike digital advertising and do not trust it. Hence a call from some of the UK’s biggest advertisers for tech platforms to set up an independent body to enforce common standards on content.

Pressure from advertisers will only go so far, though. At this stage, Unilever and those who share its frustrations still have no realistic alternative.

The latest results from Twitter and Snapchat have done something to revive sagging hopes that they might provide competition for the Google/Facebook duopoly in the long term. Snap presents itself as a safer environment through its offer of curated news. Advertisers will do what they can to foster this nascent competition. They will also seek to work with Amazon. More product searches already take place on Amazon than Google, and the ecommerce company is now looking to push deeper into online advertising.

But the others are still minnows next to the Facebook and Google duopoly — which was set to attract more than 80 per cent of global spending on digital advertising outside China last year. With hindsight, Google’s 2008 acquisition of DoubleClick, the automated ad exchange, was a defining moment, underpinning Google’s dominance in the sale of display ads. Competition authorities, who approved the acquisition, now need to be sure the duopoly is working in consumers’ interests.

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