(JTA) – Britain’s Labour Party downgraded its representation at an event celebrating a milestone of Zionism, which Prime Minister Theresa May she would attend “with pride.” Labour leader Jeremy Corbyn, who is a strong supporter of the Palestinian cause, declined an invitation to next week’s dinner commemorating 100 years since the Balfour Declaration, which Israeli Prime Minister Benjamin Netanyahu will attend in London as May’s guest, The Times of London reported Sunday.

In the 1917 declaration, named after then-foreign secretary Arthur Balfour and obtained on Nov. 2 that year after long talks with Zionist leaders, the British government vowed to help establish a national home for the Jewish people in the Land of Israel without jeopardizing the rights of other area inhabitants. “We are proud of the role that we played in the creation of the State of Israel and we will certainly mark the centenary with pride,” May said in the British parliament last week. “I am also pleased that good trade relations and other relations that we have with Israel we are building on and enhancing.”

Representing Labour at the event instead of Corbyn, who did not specify his reason for not attending, will be the party’s shadow foreign secretary, Emily Thornberry. Last month she represented Labour at a Friends of Israel event in Corbyn’s stead. The British pro-Israel group and The Jewish News newspaper of London are organizing a conference on the Balfour Declaration slated to take place at Westminster next week with senior British and Israeli politicians, including the head of Israel’s Labor party, Isaac Herzog. Corbyn will not be attending the conference either, organizers told JTA. Since his election to head Labour in 2015, Corbyn, a hard-left politician, has been fighting allegations that his alleged hostility toward Israel and purported tolerance to vitriol against it was encouraging expressions of antisemitism in his party’s ranks and among his far-left supporters. The main organization of British Jewry, the Board of Deputies of British Jews, accused Corbyn of whitewashing what it called Labour’s antisemitism problem under Corbyn. Corbyn has vowed to expel any Labour member caught making racist comments, including about Jews. Dozens of Labour members were ejected from the party for this reason, but others have been readmitted, left in place or merely temporarily suspended.