On 18 March 1939 a 10-year-old Jewish boy was woken in the middle of the night by noises from the streets of Ostrava, a city in what was then Czechoslovakia. Peering out of the window, he saw the German troops marching into the town square.

A few days later, his mother and teenage sisters waved him off on a train as he escaped to England. He never saw them again. Rounded up and sent first to a ghetto, they were murdered in Treblinka on 5 October 1942. Countless other relatives were also killed in the Holocaust.

I'm ashamed at the way my party is offending Jews, says Labour MP Read more

He eventually became a teacher in Dudley, in the West Midlands, and brought up four children, the second one of whom is me. I grew up listening to my dad telling me about the Holocaust and about the evils of racism. That motivated me to join the Labour party when I was a teenager, and the first thing I did when I became an MP was to lead a campaign to drive out the BNP from Dudley.

So am I upset about antisemitism in the Labour party? Yes, I am. And I am upset as well by the leadership’s refusal to deal with it properly. I’ve been told I am being investigated by the party for my conduct. But did I scream swearwords of abuse, as has been alleged? No, I did not.

Corbyn was not my choice to lead our party, but do people really think I'm so worried that I’d invent all this?

I am shocked and ashamed that a party that has had such a proud tradition of fighting racism has caused huge offence and distress to the Jewish community.

Under Jeremy Corbyn’s leadership, some – a minority – go way beyond legitimate and passionately held views about the plight of the Palestinians and tip over into antisemitism.

But for others it is much more fundamental, whether it is Ken Livingstone’s nonsense about Adolf Hitler, legitimising the myth that Jews were the chief financiers of the slave trade, or outrageous comparisons between the actions of Israel and the crimes of the Nazis. Jewish MPs – particularly women – have been subjected to the most horrendous abuse. And let us not forget that this crisis was triggered by the shocking discovery that Corbyn had defended a grotesque racist caricature – that had nothing to do with Israel at all.

You would have hoped they would have listened when the Jewish Labour Movement, the Jewish Leadership Council, the Board of Deputies and many other Jewish community groups said enough was enough, at that unprecedented demonstration in Parliament Square. I know one woman in her eighties, imprisoned by the Nazis as a child, who was there. Think about that: a woman who had been in Auschwitz at the first political demonstration in her life. She was protesting against us, but still the leadership didn’t listen.

More than 60 rabbis representing every strand of their faith pleaded with the Labour party to adopt the standard definition of antisemitism and all its examples. The Chief Rabbi warned that failing to do so would send “an unprecedented message of contempt” to British Jews; but even that fell on deaf ears as the Labour leadership insisted it knew more about antisemitism than all of them.

Let’s lay one lie to rest: the International Holocaust Remembrance Alliance definition of antisemitism does not close down criticism of Israel. It was developed to ensure a common policing and legal approach to a growing wave of attacks on Jewish people in Europe. It explicitly says that “criticism of Israel similar to that levelled against any other country cannot be regarded as antisemitic”. It allows Israeli policies and practices to be described as racist and doesn’t mention boycotts.

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The way the leadership weakened the IHRA examples will make it much harder to deal with antisemitism. First, for example, Labour members can now describe the establishment of Israel – not just the actions of the government, the decisions of its parliament or the behaviour of its military, but Israel’s very existence – as a racist endeavour. Second, a member could call Zionists “Nazis” and simply be warned instead of facing proper sanctions. Third, the party must find evidence of racist intent, which will be very difficult to establish.

Let’s nail another lie: it is grotesque to claim this is all being whipped up – or “weaponised” – to undermine Corbyn’s leadership. Everyone knows that he was never my choice to lead our party, but do people really think I am so worried about his plans to nationalise the railways that I’d invent all this? It is actually the other way round. It is because he has spent his entire time in politics on the fringes of the Labour party, supporting and defending all sorts of extremists and in some cases, antisemites, that I thought he should not be our leader.

I was worried that he would turn what was a mainstream social democratic party into something much more extreme, and I believe this crisis shows that is exactly what has happened. Under his leadership, we have become a different party from the one I joined as a teenager to fight racism.

• Ian Austin is Labour MP for Dudley North