The move comes after adverts were displayed alongside inappropriate material. The Government has called Google representatives to the Cabinet Office to discuss the issue.
Meanwhile, the Guardian newspaper found its adverts displayed alongside a range of extremist YouTube videos.
Other organisations are said to have been impacted, including the BBC, Transport for London and Channel 4. The issue seems to have been caused by Google's AdX – an automated system for buying and selling online advertising.
Sources: The Guardian; Business Insider.