The London-based Community Security Trust, which monitors anti-Semitism and works to safeguard the Jewish community in Britain, said 250 anti-Semitic incidents were recorded in the four weeks after Dec. 27, when Israel launched attacks on Gaza to stop Hamas rocket attacks.
That compares to 40 incidents from the same period the year before.
Dave Rich, a spokesman for the trust, said Jews in Britain are unfairly seen as local representatives of Israel—a view that fuels some of the anti-Semitic attacks.
"This is racism," he said. "And like all forms of racism, it is unacceptable."
The trust said crimes included assaults, damage to Jewish property, threats, hate mail, verbal abuse and anti-Semitic graffiti.
Police figures echo this rise. London police have recorded about three times the number of anti-Semitic incidents from Dec. 27 to Feb. 3 as compared to the same period last year. Though some of that increase came from a change in the way the statistics were kept, the data still reflected a surge in incidents in the capital.
Around Europe, several attacks were reported against Jews and synagogues in France, Sweden and Belgium in the weeks after the Israeli offensive, Rich said.
The figures were released before an international conference Monday in London on tackling anti-Semitism.