Deputy Labour leader Tom Watson has said he is "ashamed of the recent cases of antisemitism in my party".
In a Yom HaShoah message to the Jewish Labour Movement, Mr Watson said he was working with the JLM and the Jewish community "to ensure that racists and antisemites have no place in British politics. Together with many colleagues, I am backing the JLM proposals for tougher rules.
"In Mein Kampf, Hitler's hateful screed of an autobiography, he claims that Zionism is a scam. Jews don't really want a state, he claimed. It's just another Jewish plot to set up a 'criminal base' from which to control the world. Much of the language from today's anti-Zionism makes exactly the same claims."
Mr Watson went on that Israel was testimony to Hitler's ultimate failure, as was Britain's "vibrant, integrated [and] positive" Jewish community, which contributed greatly to the country.
As deputy leader, he would "fight to ensure that Britain's Jews always feel safe as a key part of this country and my party. I will fight to ensure that Zionism is not used as a term of abuse. Or as a code word for Jews. I will fight to ensure that the right to Jewish national self-determination is preserved and respected."
Mr Watson's comments came as details emerged of a Labour MP suggesting that a Labour government could make an historical apology for the creation of Israel.
Martin Mayer, a Unite union representative on Labour's NEC, sent an email on May 2 titled "How Israel lobby manufactured UK Labour party's antisemitism crisis". In it, he accused "Labour's Blairite right wing" of using "the smear of antisemitism to undermine Jeremy Corbyn's leadership".
London's new Mayor, Sadiq Khan, will attend today's main UK Yom HaShoah commemoration. He said he was honoured that the event would be his first public engagement.