Meanwhile home secretary Amber Rudd, writing in the Telegraph, warned the tech firms must do more in the wake of the terrorist attack on parliament.
"Each attack confirms again the role that the internet is playing in serving as a conduit, inciting and inspiring violence, and spreading extremist ideology of all kinds," she said.
"But we can’t do it by ourselves. We need the help of social media companies, the Googles, the Twitters, the Facebooks of this world. And the smaller ones, too: platforms such as Telegram, Wordpress and Justpaste.it."
Both ministers called on the firms to take a more proactive approach to finding extremist material.
None of the tech companies proactively look for such content, acting only when thy are alerted by others who have flagged it. But they have also been criticised for not acting fast enough to remove it when issues have been raised.
"They need to develop new systems and algorithms to detect this stuff and remove it. They are not acting when they are tipped off," said Johnson.
Rudd said: "We need them to take a more proactive and leading role in tackling the terrorist abuse of their platforms. We need them to develop further technology solutions. We need them to set up an industry-wide forum to address the global threat."
She will meet with the firms this week to ask them to do more.
It comes as the advertising boycott of Google spread further, with several US brands pulling their spending from YouTube. Numerous brands in the UK pulled advertising last week after adverts were found next to extremist content.
Late on Friday Moody's warned the loss of notable advertisers from YouTube is credit negative for parent company Alphabet, but does not impact its AA2 rating.
Google has promised to better tackle such content and give advertisers greater controls over where they appear, but stopped short of saying it will proactively police it. More than 400 hours of video is uploaded to YouTube every minute.
Alphabet chairman Eric Schmidt is the most high-profile tech executive yet to weigh in on the matter. He told US media late last week that it may not be able to guarantee that adverts won't appear against offensive content.