Mr Umunna also accused party General Secretary Jennie Formby of “misleading” MPs earlier this month when she claimed that the party’s new code of conduct on antisemitism had relied upon the findings of Home Affairs Select Committee report into the issue, of which Mr Umunna was a member.
The committee's report into antisemitism was widely praised by the Jewish community after it was published in 2016.
Mr Umunna said: "The response to the Committee’s engagement with the Jewish community, and to its report, stands in stark contrast to both the party’s engagement with the community and to how the Chakrabarti Report was received. Whereas the Committee properly consulted Jewish community groups, the party has not.”
He added: "Unlike the Committee, the party’s Code has adopted just seven of the IHRA examples. It has not adopted the examples in full and instead has chosen to produce its own version of the examples it does not list.”
Mr Umunna said he sent out his email on Monday afternoon to the PLP over fears that the letter Ms Formby sent them on July 9 was inaccurate.
He said he did “not feel the GS’s letter accurately reflects the authorship of (the Home Affairs Select Committee's) report and also may give a misleading impression of its contents”.
He said the Home Affairs Select Committee had “endorsed the use of the definition of racism set out in the Macpherson Report into the botched police investigation of the murder of Stephen Lawrence".
The Macepherson principle defines racism as an incident "perceived to be racist by the victim or any other person", he noted.
"As such, the perceptions of Jewish people—both collectively and individually, as an alleged victim—should be the starting point of any investigation into antisemitism," Mr Umunna wrote.
He described how the commitee took evidence from then Board President Jonathan Arkush, Chief Rabbi Ephraim Mirvis, then Jewish Leadership Council chairman Sir Mick Davis and Mark Gardner of the Community Security Trust.
Mr Umunna said: “We noted the difference between the use of the Macpherson definition for recording purposes and the tests required to be fulfilled in criminal and civil legal actions pertaining to racism and discrimination.”
He denied Ms Formby’s suggestion that the committee criticised some of the examples in the IHRA definition.
Mr Umunna wrote the committee had suggested adding statements to clarify: “It is not anti-Semitic to criticise the Government of Israel, without additional evidence to suggest anti-Semitic intent; It is not antisemitic to hold the Israeli Government to the same standards as other liberal democracies, or to take a particular interest in the Israeli Government’s policies or actions, without additional evidence to suggest antisemitic intent.”
Mr Umunna writes in his letter to MPs: "I was surprised to see the Committee’s report relied on and cited by the GS because when it was published, in its official response at the time, not only did the party make basic factual inaccuracies about our report’s contents but we were accused of using the issue of antisemitism as a 'weapon' for political purposes.
“Coming from a family which has had direct experience of racism, I found this to be grossly insulting and offensive.”
Mr Umunna’s comments come as 68 British Rabbis from across the denominational spectrum signed a letter urging Labour “to listen to the Jewish community, adopt the full and unamended International Holocaust Remembrance Alliance (IHRA) definition of antisemitism including its examples.”
The letter was published in the Guardian ahead of Tuesday’s national executive committee (NEC) meeting where the new code of conduct is due to be voted on.
Among the signatories were Rabbi Dr Harvey Belovski, Senior Rabbi, Golders Green Synagogue and Vice-Chair, Rabbinical Council of the United Synagogue , Rabbi Joseph Dweck, Senior Rabbi, Spanish and Portuguese Sephardi Community of the UK, Rabbi Laura Janner-Klausner, Senior Rabbi to Reform Judaism and Rabbi Nicky Liss, Highgate Synagogue and Chair, Rabbinical Council of the United Synagogue.
