Labour’s general secretary has accused deputy leader Tom Watson of being “irresponsible” for criticising the way the party has dealt with anti-Semitism.
Mr Watson criticised Labour and Jennie Formby, a close ally of Jeremy Corbyn, following a BBC Panorama investigation.
Ms Formby has written to him to say his comments risked “exacerbating” fears in the Jewish community.
She acknowledged anti-Semitism was a “real problem” in the party but said steps had been taken to tackle it.
‘Traducing my reputation’
The Panorama investigation, broadcast on Wednesday, featured claims from ex-party officials that senior Labour figures had interfered in the disciplinary process of dealing with accusations of anti-Semitism.
This included allegations that officials brought in by Ms Formby “overruled” some of their disciplinary decisions and “downgraded” punishments to a “slap on the wrist”.
The disputes team is supposed to operate independently from the party’s political structures, including the leader’s office.
In the wake of the programme, Mr Watson demanded that the party publish its submission to a formal inquiry into the issue.
In a letter to Ms Formby, he said the response to the UK’s equality watchdog the Equality and Human Rights Commission (EHRC) had been “withheld” from the party’s executive.
In reply, Ms Formby said Mr Watson was abusing his “considerable platform” to “denigrate” the progress that had been made in combating anti-Semitism.
“Furthermore, traducing my reputation and publicly attacking me when you know I am undergoing chemotherapy and am unable to respond in the media, is another example of the inappropriate way in which you choose to discuss this issue,” she wrote.
Ms Formby said she was “very concerned” by the distress suffered by some former staff members shown in the Panorama documentary, but added that “we were not made aware of these issues at the time”.
She also said she had offered Mr Watson the chance to view the document sent to the anti-Semitism inquiry and denied accusations that she had deleted emails relating to cases of anti-Semitism.
“By choosing to ignore the steps taken by this party, and commenting so uncritically about the Panorama programme, you are complicit in creating a perception that anti-Semitism is more prevalent in the Labour Party than wider society,” Ms Formby added.
Earlier, Mr Watson had accused some in the Labour Party of attempting to discredit the former staff members who took part in the Panorama documentary.
He called for greater transparency on the issue, adding: “Only sunlight can disinfect Labour of anti-Semitism now.”
In response, shadow home secretary Diane Abbott, another close ally of the Labour leader, tweeted that Mr Watson was “very wrong” to imply that Ms Formby was “dealing with the matter with anything less than her usual professionalism”.
The EHRC launched a formal investigation in May into whether Labour had “unlawfully discriminated against, harassed or victimised people because they are Jewish”.
The Jewish Labour Movement said on Thursday that more than 30 whistleblowers, including current Labour staff, would submit evidence to the inquiry.
The party has been engulfed in a long-running dispute over the issue, which has led nine MPs and three peers to leave the party.
The leadership has been accused of failing to get to grips with the problem, with allegations of hundreds of complaints against members remaining unresolved.
Labour said it “completely” rejected any claims it was anti-Semitic.
It also accused the Panorama programme of being a “seriously inaccurate, politically one-sided polemic, which breached basic journalistic standards, invented quotes and edited emails to change their meaning”.