The Green London mayoral candidate has described her frustration that a motion urging the party to adopt the IHRA definition on antisemitism will not be debated at the party’s conference amid concerns over how it would apply to disciplinary cases.

Speaking at a JW3 event on Wednesday, Sian Berry said she had co-sponsored the motion but it was deemed out of order.

"That’s really frustrating to me because we didn’t get another chance to re-write it to be in order. So it is isn’t going to the current conference that we’re about to have,” Ms Berry said.

“I’ve been trying to push the IHRA definition through, I see no problem with signing up to it. I signed up to it as a Camden Councillor. I would really like the Greens to pass this.”

She added: “I go every year to Holocaust Memorial Day events. Survivors from different genocides will talk about people suddenly turning against them.

"This is because of wider, simmering prejudice that’s allowed to fester in a society. And that’s why we need to sign up to the IHRA definition.

"So that we can push down, as a society, on the kind of prejudice that can suddenly switch. Jewish people are the ones we must listen to on this the absolute hardest because of your history.”

Ms Berry also said she believed IHRA “gives some clarity on ways you can oppose Israeli Government particular policies and clarity on how not to behave in that situation. It gives you clarity on what is prejudice and where the line is”.

She said concerns about free speech issues IHRA were “unfounded.”

“There is quite a lot of clarity in the definition,” said Ms Berry. “I can’t see the problem. As a practical guide, and we have to be practical, the definition as written is usable and fine. We need to be having that debate.”

Ms Berry, who is also co-leader of the party, revealed that she had concerns about the anti-Israel BDS movement but still backed such campaigns in certain situations.

She said: “I come from an issue-based campaigning background and I can totally see that BDS as a whole thing, it could easily be a vector for antisemitism and prejudice against Israel more generally.

“But I can see that there is potential worth in a campaign focussed particularly on individual companies that were involved particularly in military action and particular, for example, construction projects in particular settlements.

"That would be a valid campaign to run. Every single tactic you use must be examined for its benefits and costs.”

The party's spring conference is due to take place in Brighton from March 20 to 22.

All candidates for the Mayoral elections, which take place on May 7, are taking part in the weekly breakfast events at JW3 organised by the London Jewish Forum, the Jewish Leadership Council.

Also aiming to topple Mayor Sadiq Khan are Siobhan Benita for the Liberal Democrats, Shaun Bailey for the Conservatives and Rory Stewart, Count Binface and Drillminister as Independents.