European Jewish leaders anxious about the “massive growth” in online anti-Semitism have welcomed a new internet code of conduct agreed between Brussels and tech giants such as Facebook, Twitter and Google.

The European Commission’s new Code of Conduct on Countering Illegal Hate Speech Online includes a pledge by the companies to review “the majority” of abuse reports within 24 hours, and to clamp down on illegal and xenophobic content.

Microsoft and YouTube (owned by Google) also signed up, as Vera Jourova, the European Union’s Commissioner for Justice, said recent terror attacks had “reminded us of the urgent need to address illegal online hate speech”.

She added: “Social media is unfortunately one of the tools that terrorist groups use to radicalise young people and racists use to spread violence and hatred. This agreement is an important step forward to ensure that the internet remains a place of free and democratic expression, where European values and laws are respected.”

Rabbi Pinchas Goldschmidt of the Conference of European Rabbis agreed, saying: “Internet hate leads to a culture of fear. We hope [the Code] will be the first step in combatting that culture and making internet users accountable.”

Moshe Kantor of the European Jewish Congress said there had been “a massive growth of online hate speech and incitement in recent years” and that governments and law enforcement agencies should co-operate on the issue.

“Many of those who have shed blood on the streets of Europe in recent years have been indoctrinated online,” he said. “Hopefully this agreement can cut off a means of recruitment into extremist organizations.”

Signatories Twitter and Facebook are the two most popular social media sites in Europe, with the latter owning Instagram and WhatsApp, and both recognised the need to concerted action.

However Twitter’s head of public policy for Europe warned that while the company was happy to help, “there is a clear distinction between freedom of expression and conduct that incites violence and hate”.