Boris Johnson has attacked internet giants for their "disgusting" failure to remove extremist material from the web.
The Foreign Secretary also called on internet providers and social media companies like Facebook and Twitter to develop new technology to detect and remove jihadist and other extreme material.
He accused them of "not acting when they are tipped off", adding in an interview with the Sunday Times: "I'm furious about it.
"It's disgusting.
"They need to stop just making money out of prurient violent material."
Mr Johnson echoed Prime Minister Theresa May in saying internet companies need to prevent terror and hate being spread in cyberspace.
Information on how to mount a terror attack was found to be easily accessible online in the wake of the Westminster atrocity on Wednesday.
Before the attack took place, Google had already been forced to promise it would take a ''tougher stance'' on hateful content after an outcry and boycotts from advertisers over its content appearing alongside extreme material.
Mr Johnson said: "They are not acting when they are tipped off.
"Evil flourishes when good men do nothing - and that's what's happening here.
"They are putting up adverts next to it."
His comments were echoed by Home Secretary Amber Rudd, who named and shamed lesser known websites like Telegram, Wordpress and Justpaste.it, as she widened the Government's criticism of online firms.
"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 wrote in the Sunday Telegraph.
"But we can't tackle it by ourselves ... We need (social media companies) to take a more proactive and leading role in tackling the terrorist abuse of their platforms."