BBC Panorama's Is Labour Anti-Semitic? programme explores both the facts and speculation surrounding the anti-Semitism scandal within Jeremy Corbyn's party.
But who are Seumas Milne and Jennie Formby, the aides featured in the documentary? Here's what you need to know.
Who is Seumas Milne?
Seumas Milne is Mr Corbyn's communications chief and a former Guardian journalist who worked for the paper for more than 30 years.
He is the author of the book The Enemy Within: The Secret War Against the Miners, focusing on the strikes during the mid-1980s.
He was appointed the Labour Party's Executive Director of Strategy and Communications in October 2015, under new Labour Leader Jeremy Corbyn, initially on leave from The Guardian.
In January 2017 he left the paper to work for the party permanently.
He reportedly told officials the party was "muddling up political disputes with racism" and must review processes.
It was claimed in a new documentary that Mr Milne laughed when advised by a long-serving party official about what Mr Corbyn should do to tackle anti-Semitism in the party.
Who is Jennie Formby?
Jennie Formby is a British trade unionist and politician.
She is the current General Secretary of the Labour Party, having succeeded Iain McNicol in April 2018.
She joined Labour's NEC - National Executive Committee (NEC) - the party's ruling body in 2011.
Previously, she was political director and south-east England regional secretary for Unite the Union.
She reportedly attempted to interfere in who sat on a panel examining a high-profile case.
It is claimed in a new documentary that officials brought in by Ms Formby "overruled" disciplinary decisions and "downgraded" punishments to a "slap on the wrist"
What was the BBC Panorama programme about?
Up to a dozen ex-Labour staff are said to have spoken to the BBC about how the party processes complaints, and whether senior staff intervened in cases.
The explosive documentary will reveal how some of Mr Corbyn’s closest aides are said to have intervened to stop anti-Semites being kicked out and laughed off calls to tackle the crisis.
Eight ex-Labour staffers broke restrictive gagging orders to lay bare the sheer scale of racism in the party.
They told BBC Panorama how the party was hit by a flood of cases of Jew-baiting racism after Mr Corbyn became leader in 2015.
The party's storm over how it deals with anti-Semitism allegations has now been swirling for more than three years - and the Labour boss has been repeatedly accused of not taking the problem seriously enough.
List of names of interviewees and dates of service:
Kat Buckingham, Head of Disputes and Discipline 2015 – 2017
Mike Creighton, Director of Audit and Risk 2009-2017
Sam Matthews, Head of Disputes 2016-2018
Ben Westerman, Investigations Officer 2016-2017
Martha Robinson, Complaints Administrator 2018-2019
Dan Hogan, Investigations Officer 2016-2018
Louise Withers Green, Disputes Officer 2017-2018
Baron Iain McNicol, General Secretary of the Labour Party 2011-2018
Labour have furiously denied the allegations and written to the director general of the BBC accusing the corporation of bias.
A Labour spokesman said the party is absolutely committed to tackling anti-Semitism.
In response to the Panorama programme, a Labour Party spokesperson said: “The Labour Party at all levels is implacably opposed to anti-Semitism and is determined to root out this social cancer from our movement and society. Labour stands in solidarity with Jewish people and is fully committed to the support, defence and celebration of the Jewish community and its organisations.
“Jeremy Corbyn has a long and principled record of solidarity with the Palestinian people and it is false to claim that he has associated with extremist groups. Jeremy Corbyn has proactively addressed anti-Semitism within the Party in direct communications to the Party membership, in articles, speeches, videos and interviews.
“The Leader’s Office did not intervene. These former disaffected employees sought the view of staff in the Leader’s Office, which was compiled with in good faith.
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"These disaffected former officials include those who have always opposed Jeremy Corbyn’s leadership, worked to actively undermine it, and have both personal and political axes to grind. It is simply untrue to say that there were any significant number of disagreements about what constituted anti-Semitism.
“The emails… are simply about ensuring the NCC is held accountable for the length of time they take to hear cases and about protecting the Party against any successful legal challenge on the basis of perceived bias if the same panel is used in high profile cases.
“Labour is taking decisive action against anti-Semitism, doubling the number of staff dedicated to dealing with complaints and cases. And since Jennie Formby became General Secretary, the rate at which anti-Semitism cases have been dealt with has increased four-fold.”