Google, Alphabet Inc.'s main revenue engine, announced that it will change its advertising policies after several major brands removed ads from the platform because they appeared alongside offensive content, such as videos promoting terrorism or anti-Semitism.

The US company said in a blog entry that it would give advertisers more control over where their ads appear on YouTube, the video sharing service they own, and on the Google Display Network, which posts ads on third-party websites and Next to the results of the search engines.

The announcement came after the British government and the Guardian newspaper stepped up pressure on YouTube to watch the content on its platform, removing ads from the video site because they appeared alongside clips they deemed inappropriate.

The decision to withdraw the ads from Google came after an investigation by the Times of London, which revealed that ads from many large companies and the UK government appeared alongside content from people such as white nationalist David Duke and the pastor Steven Anderson, who praised the killing of 49 people in a gay nightclub.

Ronan Harris, chief executive of Google in the UK, said in the blog post that last year Google eliminated nearly 2 billion offensive ads from its platforms and also blacklisted 100,000 publishers of the AdSense program company. Despite this, Harris wrote on the blog, "we do not always do it right."

He said Google heard "loud and clear from its advertisers that we can offer simpler and more forceful ways to prevent their ads from appearing alongside contentious content."

The company will now review its policies and said it would make changes "in the coming weeks" to prevent customer ads from appearing on objectionable web sites or next to offensive videos, Harris said.

The ads appeared "alongside hateful and extremist videos," prompting Guardian News & Media to stop advertising through Google, the parent company of YouTube, the British publisher said in an e-mailed statement Friday. The UK government said it has suspended advertising on YouTube until the site can guarantee that it will not be placed next to content it does not approve.

"Google is responsible for ensuring that the high standards applied to government advertising are met and that ads do not appear alongside inappropriate content," the UK government said in an e-mailed statement. "We have set a temporary restriction on our YouTube advertising spending the assurances from Google that government messages can be distributed in a secure and appropriate manner."

The boycott reveals a growing adverse reaction against the so-called programmatic trade, which automates the buying and selling of online advertising, and against social media providers who are accused of not striving hard enough to deal with hatred scattered on their platforms.