The food giant Nestle and several other big companies have pulled their adverts from YouTube following claims they appeared next to offensive content.
It comes after a vlogger accused YouTube of failing to stop a "soft-core paedophilia ring" on its platform.
The vlogger said the firm made it easy to find videos of young girls, even though comments clearly showed that viewers were sexualising the videos.
YouTube said it took "immediate action" to delete the offending accounts.
The firm, which shares a parent company with Google, has been criticised for not removing offensive content fast enough in the past.
Vlogger Matt Watson made the allegations in a video posted on YouTube that has been watched nearly two million times.
He explained the videos themselves were not sexual, but that commentators had flagged moments when girls appeared in compromising positions - such as performing gymnastics or posing in front of a mirror.
One watch spurred YouTube's algorithm to recommend similar videos, some of which ran next to ads from firms such as Disney and Nestle.
A Nestle spokeswoman said the food maker had decided to "pause" YouTube advertising globally while the issue was investigated.
"We will revise our decision upon completion of current measures being taken ... to ensure Nestlé advertising standards are met," she said.
Epic Games, the maker of the Fortnite video game, also said it had halted ads on the platform.
It said: "Through our advertising agency, we have reached out to Google/YouTube to determine actions they'll take to eliminate this type of content from their service."
Disney and German food company Dr August Oetker also took action, according to Bloomberg, which first reported the story.
In its statement YouTube said: "Any content - including comments - that endangers minors is abhorrent and we have clear policies prohibiting this on YouTube," the company said.
"There's more to be done, and we continue to work to improve and catch abuse more quickly."
It is not the first time YouTube has run into this kind of problem.
Part of its system for reporting sexualised comments left on children's videos was not functioning correctly for more than a year, moderators said back in 2017.
In 2017, the company apologised after adverts from government agencies and companies such as Marks & Spencer and Audi appeared next to videos from supporters of extremist groups on YouTube's platform.
At the time, those companies also pulled ads amid the controversy.
Despite growing pressure on Google and YouTube to crack down on offensive content, the firms' advertising revenues continue to thrive.
Their parent company, Alphabet, earned almost $137bn (£105bn) in revenue in 2018, up 23% from the prior year.