It was in February, while on holiday with her former Labour colleagues in Berlin, that Louise Withers Green decided she had to speak out about her role in investigating antisemitism in the party.

The former disputes officer visited the German capital with a number of ex-staffers, all of whom had quit working for the party. Being in the city that had been at the heart of anti-Jewish genocide convinced them they had to take public action.

“I had to think about the sort of person I wanted to be when I died,” she said in her first interview since she was revealed as one of eight whistleblowers who spoke to the BBC’s Panorama for a programme transmitted on Wednesday night.

“I wish there were more people that would speak out when things weren’t right, speak out against racism. Even though this might be really horrible, in 30 years I’ll be really proud of myself that I’ve done it.”

She and her ex-colleagues took the trip after several former staffers suffered serious mental health issues during their time in the complaints unit.

“We had all recovered to an extent, so we went to Berlin and we were surrounded suddenly by all of that history,” she said.

“We were really feeling the impact of what even just racist threats can become. Being faced with what that can lead to – it made it feel urgent that we did something.”

The 27-year-old, a former student union officer, said she had deep feelings of guilt that she had not been able to tackle antisemitism in her role at Labour.

“For the same reasons I joined the Labour party, I care still about equality, anti-racism, standing up for people who are being oppressed,” she said. “I tried internally to do them justice, that was literally my job, to ensure the party holds those values.

“I am genuinely quite scared about what the rising rhetoric of anti-Jewish racism means for Jews and for the country. The thought of things getting worse, and me not speaking out when I could, I wouldn’t have been able to live with myself.”

Withers Green started working for Labour full-time from February 2017, having joined the party three years earlier.

“I wanted to work for the party for the same reason I joined as a member, I believe and still believe the Labour party can be the greatest force for fairness, equality and anti-racism,” she said. “I was excited to play my part in that, to help the party in ways I could, to help people, to change society.”

Withers Green said she had not voted for Jeremy Corbyn in 2015 but when he was elected, she was interested to see what would happen with his leadership. “I wasn’t hostile to him … my doubts might have been more about his electoral prospects, not his politics,” she said.

Before she started her job, which included preparing cases against members facing expulsion by the party’s highest disciplinary body, the National Constitutional Committee, she said antisemitism had barely crossed her radar. “It seemed archaic, I didn’t know anything about the issue,” she said.

She said complaints of anti-Jewish racism were “far, far more” than any other form of racism or hatred but she said she began to notice “an increasingly high bar for what constituted antisemitism”.

“People I was working with would show me antisemitic things on their screens and I’d flinch – and then it was deemed not antisemitism or at least the sanctions were lessened to a warning or a reminder of conduct, which means nothing,” she said.

She said the pressure externally to deal with the issue, as well as alleged interference in the process, took a punishing toll on her mental health.

“I almost didn’t notice it creeping up on me but the atmosphere was absolutely horrendous. I ended up really quite unwell, having to leave because I was too depressed and anxious to go into work, which is not a problem I had ever struggled with before,” she said.

Withers Green was signed off sick in June 2018. “It was like being pincered, it felt like the leader’s office were blaming us for not having dealt with antisemitism but also completely hindering our ability to do so,” she said.

“One day I woke up and I couldn’t get out of bed. I have never, ever had that before. I only realised then how bad it had been. I knew I couldn’t put myself back in there.”

It was at that point that she agreed to sign a non-disclosure agreement to leave without working her notice. “I had to see a lawyer before I signed but I still didn’t feel I had a choice. It was what I needed to do to leave,” she said.

Withers Green said she knew she could potentially face legal action for breaking the NDA. “That’s a risk,” she said. Short-term, she is more worried about being the target of trolls, having seen the kind of abuse that can occur, though she is not on Twitter.

“I’m scared, yes. I have literally been in the department which saw the abuse people received. And I absolutely never thought I would be the target,” she said.

“But I have the opportunity to speak out and not many other people have that experience, I’m one of the only people who can.”

A Labour spokesperson robustly rejected the allegations in the documentary, saying the party was “implacably opposed to antisemitism and is determined to root out this social cancer from our movement and society”.

The spokesperson added that Corbyn had “proactively addressed antisemitism within the party in direct communications to the party membership, in articles, speeches, videos and interviews”.

Withers Green said she remains a member of the party, but said she had no confidence in change while Corbyn remained leader.

“I think Corbyn is ultimately responsible. Unless he has been deceived entirely, the buck has to stop somewhere,” she said.

“I don’t believe anyone that has interfered in any of the cases should be still in position. If you are willing to do that, then you are crossing a line. Protecting your mates above the Labour party’s core values, if you are willing to do that, there is no redeeming that, they should step aside.

“I am hopeful and I believe there is redemption for the party. I want to see the Labour party as the extraordinary force for good that I know it can be, I want that back.”