Internet giants Facebook, Microsoft, Twitter and YouTube are not doing enough to fight online hate speech despite "moving in the right direction", the European Commission said on Tuesday.
All four signed an EU code of conduct in May aimed at combatting Internet hate speech.
"It is our duty to protect people in Europe from incitement to hatred and violence online," European commissioner for justice, consumers and gender equality Vera Jourova said.
"This is the common goal of the code of conduct. The last weeks and months have shown that social media companies need to live up to their important role and take up their share of responsibility when it comes to phenomena like online radicalisation, illegal hate speech or fake news.
"While IT Companies are moving in the right direction, the first results show that the IT companies will need to do more to make it a success."
The four IT companies had committed to review notifications of potential hate speech within 24 hours.
But the Commission noted in a report published on Tuesday that among 600 notifications made, only 28 percent led to the removal of content while just 40 percent were treated within 24 hours.
Another 43 percent were reviewed in under 48 hours.
The notifications were sent to the IT companies by a group of 12 NGOs from nine different countries who analysed notification responses over a six week period.
YouTube was also most active in removing content on 48 percent of cases compared to Twitter's 19 percent.