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Labour has launched "education materials" to help its members confront anti-Semitism in the party.
Jeremy Corbyn said only a "small number" of Labour members held anti-Semitic views, but a larger number do not recognise stereotypes and conspiracy theories.
Nine MPs and three peers have left Labour over its handling of anti-Semitism allegations among members.
The shadow cabinet is due to discuss the issue at a meeting on Monday.
In a letter to members, Mr Corbyn said the new material would be the first in a series on "a number of specific forms of racism and bigotry".
He said the scale of the problem within Labour had been exaggerated by "some of the media", but the party was "not immune" from the problem of anti-Jewish hatred.
The new party materials include a leaflet and website page on the history of anti-Semitism, Zionism, and anti-Jewish conspiracy theories.
"The worst cases of anti-Semitism in our party have included Holocaust denial, crude Jewish-banker stereotypes, conspiracy theories blaming Israel for 9/11 or every war on the Rothschild family", he said.
"So please engage with the materials we are producing [...] so our movement can be the strongest anti-racist force in our country."
Also on Monday, Labour peers will consider a motion calling for a no-confidence vote in Mr Corbyn over his leadership on the anti-Semitism issue.
If passed, a ballot of all Labour peers will follow.
Earlier this month, the BBC's Panorama revealed claims from a number of former party officials that some of Mr Corbyn's closest allies tried to interfere in disciplinary processes involving allegations of anti-Semitism.
As well as calls for an investigation into the claims made in the BBC programme, the Labour leadership is also under pressure to adopt an external complaints process, and automatically exclude members where there is "irrefutable evidence" of racism.
Ahead of the shadow cabinet meeting on Monday, the Jewish Labour Movement (JLM) wrote to members urging them to show "real leadership" on the issue.
"JLM, our supporters and the wider Jewish community despair at the lack of resolve, the repetition of worn words with no effort or intention to act."
Labour has rejected claims of interference in its disciplinary processes and described the Panorama programme as "seriously inaccurate" and "politically one-sided".
In a statement, it said: "Since Jennie Formby became general secretary the rate at which anti-Semitism cases have been dealt with has increased more than four-fold.
"We will build on the improvements to our procedures made under Jennie Formby, and continue to act against this repugnant form of racism."