Civic and religious leaders are concerned about a recent rise in anti-Jewish attacks and incidents in Britain, linked to the exploitation by racists of feelings about the current hostilities in Gaza.
Similar concerns have been raised in Sweden, Germany and other parts of Europe.
The Community Security Trust (CST), which works to protect and support Jewish people, has noted 24 incidents between 29 December 2008 and 6 January 2009 alone, of which 19 were in London.
These incidents included an arson attack on a synagogue in north-west London on Saturday 10 January.
CST spokeperson Mark Gardner said: "There has been a significant rise in the number of anti-Semitic incidents, especially when compared with what is usually a very quiet time of year for racist, anti-Jewish attacks."
He added: "This is how racist attacks work. You have a grinding level of however many you expect in a year, then these trigger events [such as the responde to Gaza] lead to a sudden surge."
In the attack on the synagogue, in Brondesbury, arsonists tried to smash a window, but failed because of the toughened protective glass.
Mr Gardner said: "Having been thwarted they then appear to have attempted to set the front door alight with petrol, causing some damage to the exterior of the premises. Police, CST and fire brigade attended the scene."
On New Year's Eve, a gang of youths alarmed people in Golders Green, north west London, by trying to enter Jewish shops while shouting "Jew" at individuals. Nearby, a Jewish man was pulled from his car and assaulted by three men, reports the Independent newspaper.
The Community Security Trust has also noted anti-Semitic graffiti in Jewish areas across London, with slogans sprayed on walls including "Kill Jews".
Most of the five incidents outside London were in north west England, including graffiti on one synagogue, anti-Semitic hate mail sent to another one, and "Hamas HQ" graffiti on a Jewish building in Manchester.