Many Jews in Europe say anti-Semitism is increasing, particularly on the internet, according to a survey by the EU's Fundamental Rights Agency (FRA).
The survey of 5,847 Jewish people said 66% of those who responded considered anti-Semitism to be a problem.
Three out of four respondents, 76%, believed anti-Semitism had increased over the past five years.
The survey was carried out in 2012 in eight countries which are home to about 90% of the EU's Jewish population.
Respondents in Belgium, France, Germany, Hungary, Italy, Latvia, Sweden and the United Kingdom were asked to give "their opinions and perceptions on anti-Semitic trends and anti-Semitism as a problem in everyday".
They were also asked about their personal experiences and worries about their own safety and that of family members.
There was particular concern about anti-Semitism online. About three-quarters of respondents considered that to be a problem which is getting worse.
A British woman in her 50s, quoted in the survey, said she had "experienced more anti-Semitic comments" since going on Facebook "than I ever have done throughout my whole life".
She added: "This is very dispiriting. The speed at which hostile comments and misinformation can be passed around is frightening and leads to a sense of deep unease, which may not connect with the day-to-day reality of being Jewish in a diverse society."
The survey found 29% of those surveyed had considered emigrating because of concerns about safety, with particularly high figures recorded in Hungary (48%), France (46%) and Belgium (40%).
It found one in five respondents had personally experienced at least one anti-Semitic verbal insult and/or a physical attack in the year before the survey.
Perpetrators of the most serious incidents were described as "being perceived as someone with Muslim extremist views, 27%, left-wing political views, 22%, or with right-wing views, 19%".
Respondents said the most frequent comments made by non-Jewish people in the UK were: "Israelis behave 'like Nazis' towards the Palestinians" and "Jews exploit Holocaust victimhood for their own purposes" (both 35%).
In France 52% of the Jewish people surveyed described anti-Semitism as a "very big problem" in their country, in Hungary the figure was 49%, while in the UK it was much less - 11%.
The survey showed significant differences between Western and Eastern European countries.
In Latvia, only 8% said the Israeli-Arab conflict had had a large impact on how safe they felt, but the figure rose to 28% for Germany and was as high as 73% in France.
FRA Director Morten Kjaerum said this reflected differing histories, as well as recent patterns of immigration.
"I think that there is across Europe... a traditional form of anti-Semitism that goes back in history for a long time," he said.
"But then we also see a particular sort of anti-Semitism reported by the respondents, namely the anti-Semitism which comes out of the conflict in the Middle East. And this is where you have to be careful: when do you have a legitimate critique of whatever your position may be in terms of that particular conflict and when would it be an anti-Semitic statement?"
Demand for action
The FRA said EU countries should work "urgently" to find effective ways to combat online anti-Semitism. It called on public figures to condemn anti-Semitic statements.
The President of the European Jewish Congress, Moshe Kantor, welcomed the survey, but said "the fact that a quarter of Jews are not able to express their Jewishness because of fear should be a watershed moment for the continent of Europe and the European Union."
"The Jewish reality in Europe is of great concern and the authorities need to deal with incidents of hate and intolerance in a holistic manner, to really combat these manifestations before it is too late.
"We would like to see concrete steps being taken, including creating legislation to specifically deal with anti-Semitism and racism, bolstering law enforcement agencies and ensure a zero-tolerance approach to anti-Semitism, even, and perhaps specifically, when opinion-shapers and decision-makers engage in these forms of hate," he said.