Jessica Davies:

The biggest ad buyer in the world has some serious issues with Facebook, and it wants action.

“We’re increasingly holding Facebook to account to justify the levels of investment we are putting in them,” said Robin O’Neill, managing director of digital trading for GroupM. “We continue to press them to allow us to independently verify our metrics and operate in the real world. Facebook doesn’t operate with real-world metrics. I would urge every agency to hold Facebook to account and interrogate the data that comes out from them.”

Facebook and YouTube have been plagued by negative headlines over the last year or so, either related to brand-safety issues or lack of transparency around metrics. Both companies have attempted to offer improvements: Facebook introduced new brand-safety measures as recently as this week, though advertisers weren’t wholly impressed by its efforts. Google launched Google Measurement Partners in July, which allows advertisers to verify ad delivery through a set of third parties including comScore, DoubleVerify, IAS, MOAT, Nielsen, and Kantar.