The Holocaust is one of the most well documented and researched periods in history. There are clear records of the systematic and industrial scale of the Nazi plan to murder the Jews of Europe. Not only from historians but from the Nazis themselves. Most importantly, we have the testimony of the lucky few who managed to survive whilst their families were shot into pits, deported and sent to gas chambers or simply left to starve to death.

You would therefore think that those who seek to deny or to denigrate this history would be given short shrift.

Which is why it has been all the more shocking to see the Holocaust once again called into question, and the root cause of this tragedy - antisemitism - rearing its head at a mainstream political party conference.

You only have to look at one single day with a series of deeply uncomfortable interventions by those who should know better: we had director Ken Loach suggesting that debate about whether the Holocaust happened is OK, saying “history is for all of us to discuss”; Len McCluskey, General Secretary of the Unite Union labelling concerns about antisemitism as “mood music”; and then Ken Livingstone - never one to hold back on his views on this particular topic - stating that making offensive remarks about Jews is not necessarily antisemitic…err, OK Ken.

When you have central figures making these sorts of insulting and ignorant comments, they embolden those who have only one agenda – to undermine the truth of the past and to whip up hatred against Jews today.

I think of the survivors of the Holocaust, some of whom we are fortunate to still have with us, and feel shame. After everything they suffered, they have to witness this. The pain and hurt this must cause.

How many times do we have to defend basic truths that should be considered sacrosanct? How many times do we need to explain that antisemitism is as much a form of racism as any other?

We have all been alarmed by the rise of the far-right around the world in recent months, culminating in the terrible events in Charlottesville in August. And equally we worry about the far-right gains in the German elections for the first time in decades.

Yet, it is all too easy to point the finger at events elsewhere - sometimes we need to look in our own backyards and admit where the problems lie. And there are problems here.

We need our political leaders to take a stand and say when a line has been crossed. We need to be clear that antisemitism will not be tolerated and reflected in concrete action. We need our leaders to be clear that they will not stand by as the truth of the Holocaust is undermined on their watch.

Karen Pollock MBE is Chief Executive of the Holocaust Educational Trust.