The government has removed its adverts from YouTube amid concerns they are appearing next to "inappropriate" material on the video-sharing site.
The Cabinet Office said it was seeking assurances from YouTube's owner Google that its messages would be displayed in a "safe and appropriate way" in future.
The Guardian, Channel 4 and the BBC have also pulled ads citing similar worries.
Google said it would review its controls.
The firm has been attacked by MPs in the past for not doing more to curb online hate speech.
The internet giant said it had "strict guidelines" about the placement of adverts but conceded "we don't always get it right".
A recent investigation by the Times found adverts were appearing alongside content from supporters of extremist groups, making them around £6 per 1,000 viewers, as well as making money for the company.
Ministers have summoned Google for talks at the Cabinet Office after imposing a temporary restriction on its own ads - including for military recruitment and blood donation campaigns - appearing on YouTube.