In light of the recent terror attack in London and more details emerging about chief suspect Khalid Masood's suspected radicalisation, the UK government is pulling up internet giants Facebook and Google for failing to curb extremist content.

"The two online giants can and must do more," said the Prime Minister Theresa May's spokesman James Slack. "Social media companies have a responsibility when it comes to making sure this material is not disseminated," he added.

Additionally, UK Foreign Secretary Boris Johnson – who is currently in the US – also blamed Google's search through which extremist publications can be found easily online. He noted that propaganda material is "corrupting and polluting" people and blamed social media networks for their failure to keep such content in check.

"They have got to look at the stuff that is going up on their sites. They have got to take steps to invigilate it and to take it down where they can," Johnson said as quoted by The Register.

The criticism comes at a time when Google is facing backlash from advertisers for airing their brand alongside extremist, homophobic and anti-Semitic content on YouTube. Hundreds of brands in the UK and US including GM, Starbucks, Marks and Spencer, RBS, The British Government, Walmart, Verizon and PepsiCo have pulled out from advertising on YouTube.

The Daily Mail too came down heavily on the search engine and carried a story titled, "Google, The Terrorist's Friend". The story detailed how it takes less than two minutes to find a manual on how to use a car for mass murder.

Meanwhile, police are digging into Masood's life and trying to piece together how he turned to extremism despite being labelled as a "good and popular" child in school by many of his batch mates.