Antony Lerman, the former director of the Institute for Jewish Policy Research, has defended his decision to a speak at an event organised by Jews in favour of boycotting Israel.
He said his appearance at the Jews and Palestine conference held by Jews for Boycotting Israeli Goods (JBig) in London on Saturday did not indicate support for their views.
Mr Lerman, an Israeli citizen who left JPR at the end of 2008 and is now a regular blogger on Jewish affairs for the Guardian, said: "I am not a supporter of boycotting Israel to achieve change, but I think it is a legitimate position for people to hold."
He spoke on antisemitism and the role it played "in preventing change as far as Israel/Palestine politics are concerned".
Mr Lerman, who considers himself a non-Zionist, said: "If I felt that something like this had overall underlying antisemitic intentions, I wouldn't go anywhere near it. But I know some of the people involved - I don't agree with everything they say - but I respect a lot of what they believe in, and I think it is important to engage in discussion."