Facebook, Twitter and YouTube have accelerated removals of online hate speech in the face of a potential European Union crackdown.

The EU has gone as far as to threaten social media companies with new legislation unless they increase efforts to fight the proliferation of extremist content and hate speech on their platforms.

Microsoft, Twitter, Facebook and YouTube signed a code of conduct with the EU in May 2016 to review most complaints within a 24-hour timeframe.

Instagram and Google+ will also sign up to the code, the European Commission said.

EU Justice Commissioner Vera Jourova has said that she does not want to see a 100 per cent removal rate because that could impinge on free speech.