Government adverts shown before extremist online videos
A government organisation temporarily suspended online advertising after a BBC Newsnight investigation found ads being shown before extremist videos.
Adverts for the National Citizen Service (NCS), as well as businesses, charities and the BBC were found running next to extremist videos.
Companies' and taxpayers' money may have gone to jihadi groups because of the way the sites like YouTube operate.
YouTube said it removed violent videos when they were flagged by users.
Host sites, including Youtube, share income from advertisers with the individuals or groups that provide the content.
As a result, advertisers like the National Citizen Service - run by the Cabinet Office - are potentially unwittingly funding extremists.
The National Citizen Service is a Cabinet Office programme that provides a modern-day equivalent to national service, intended to teach young people valuable skills and to help local communities.
Oxfam has also removed one of its adverts and the BBC said it may rethink its internet advertising strategy.
Newsnight found their adverts running directly before videos used to spread Islamist propaganda and encourage young people to join the conflict in Syria.
Jihadi videos are one of the main tools used by Islamic State in Iraq and the Levant (ISIS) and other groups to radicalise young Muslims.
One British jihadist in Syria, who has uploaded videos encouraging others to join the conflict, told Newsnight he considered the internet to be "half of jihad and of very great importance", saying they were waging "a war of hearts and minds".
The National Citizen Service's chief executive, Michael Lynas, said: "No National Citizen Service (NCS) video should appear before the sort of material Newsnight has highlighted.
"It is appalling and is entirely against the ethos of NCS, which brings young people from all backgrounds together, building a more cohesive, engaged and responsible society."
Mr Lynas said NCS had "immediately suspended" its advertising account while it investigated, before being told by YouTube that NCS adverts had been removed from the video.
He said the advertising campaign had been resumed with the situation kept under review.
Matt Smith, of social media advertising agency The Viral Factory, said it would not be possible for host sites to "police what is being advertised against every single video", but added: "You could say it's incumbent on YouTube to make sure that ads aren't running against questionable content."
Oxfam said it was "extremely careful" about the way its adverts were placed online with checks to ensure they did not appear "alongside content that is contrary to our values".
It added: "On sites like YouTube, these decisions are made automatically and in this instance the system has led to a placement that is not acceptable. The ad has now been removed and we will work to make sure this doesn't happen again."
The BBC said it was not currently advertising with YouTube and would consider future plans in light of the Newsnight revelations.
YouTube said it removed violent videos when they were flagged by users and terminated accounts registered by members of a "designated Foreign Terrorist Organisation".
It added: "We allow videos posted with a clear news or documentary purpose to remain on YouTube, applying warnings and age-restrictions as appropriate."
Another site, Daily Motion, which had been showing extremist videos including a beheading alongside adverts for multinational companies, thanked Newsnight for alerting it to the videos.
It added: "We have taken down the video that included graphic content, and have placed the other video, that includes no graphic content, behind a family filter (with no adverts) as a safety precaution."