Google has said its YouTube site has zero tolerance for content that incites violence or hatred following claims that household brands are unwittingly advertising on extremist posts.
An investigation by The Times found that advertisements for hundreds of companies, universities and charities have appeared on pornography and hate sites and YouTube videos created by supporters of terrorist groups such as Islamic State and Combat 18, a violent pro-Nazi faction.
The Times said an advert for the new Mercedes E-Class saloon ran next to a pro-Isis video which had been viewed more than 115,000 times, while holiday operator Sandals was advertised next to a video promoting al-Shabaab, the East African jihadist group affiliated to al Qaida.
A Marie Curie ad was seen on a video about Combat 18, while ads for Honda, Thompson Reuters, Halifax, Liverpool University and Waitrose also appeared on videos posted on YouTube containing extremist content.
The newspaper said an advert appearing alongside a YouTube video typically earns whoever posts it 7.60 US dollars (£6.05) for every 1,000 views, with some of the most popular extremist videos receiving more than one million hits.
A Google spokeswoman said: "When it comes to content on YouTube, we remove flagged videos that break our rules and have a zero tolerance policy for content that incites violence or hatred.
"Some content on YouTube may be controversial and offensive, which is why we only allow advertising against videos which fall within our advertising guidelines.
"Our partners can also choose not to appear against content they consider inappropriate, and we have a responsibility to work with the industry to help them make informed choices."
YouTube, which receives up to 400 hours of uploaded content every minute, has a designated "promotes terrorism" flag underneath every video, while advertisers can also control where their ads might appear by using a range of filter tools.
But The Times said that blacklists designed to stop advertisements from appearing next to online extremist content were "not fit for purpose".
Mercedes-Benz owner Daimler said it had asked all markets and media agencies to review, and if necessary update, lists of platforms and channels that were "not compatible with our principles".
The company said: "Daimler dissociates itself from all forms of discrimination and extremism.
"Mercedes-Benz has strict media guidelines, which our markets and our media agencies adhere to.
"These prohibit the use of platforms and channels that are not compatible with our principles, such as those with extremist or politically polarising, discriminatory, sexist or criminal content."