BBC presenter Andrew Neil has said that antisemitism on the far-left is now a "more dangerous" trend in the UK than the extremism of the "knuckle dragging" far-right.
Delivering the keynote speech at the annual Holocaust Educational Trust dinner in central London, the Daily Politics show host also launched a scathing attack on Ken Livingstone for "intentionally" attempting to link Zionism with Nazi Germany.
Warning that the scourge of antisemitism was on the increase Mr Neil said: "When I was growing up the obvious antisemites were the knuckle-draggers in the National Front. In this country what was left of the KKK in America, the Holocaust deniers like Jean-Marie Le Pen.
“Now these people and their kind are still around. But they are more marginal than they've been and they are less significant than they’ve been.
What has surprised me and what I think was entirely unpredictable was that the new development in this area is the rise of antisemitism on the far left. That is more dangerous than the knuckle dragging right."
The former Sunday Times editor told the audience, which included Home Secretary Amber Rudd, Culture Secretary Sajid Javid and former Labour shadow chancellor Ed Balls, that there had always been "a strain of antisemitism" which ran through "parts of the British intellectual left."
But turning his attention to the Mr Livingstone he said: "We have the former Labour Mayor of this city intentionally linking Zionism and Germany in the 1930s based on the ramblings of an obscure Trotskyite historian.
"There can be no bigger insult to link Zionism with Nazi Germany. We know what he was doing, it is clear as night follows day. But he is still regarded a respectable politician in this country."
Mr Neil cited the recent Labour Party conference in Brighton as example of where antisemitism was allowed to enter mainstream politics.
He said: "One person demanded the right to debate -" Holocaust, yes or no?"
"Why ask "yes or no" at a mainstream political party on the Holocaust?"
He also warned that increasingly hatred of the state of Israel, masquerading as anti-Zionism actually represented modern day antisemitism. He said: "On the far left, just as there is on the far right there is a dislike of Israel, not just a dislike, a hatred of Israel.
"When it turns into hatred beyond normal criticism of foreign policy and state conduct, which we are all free to do and which every country must be subject to, when it turns to hatred then antisemitism flourishes.
"Since the Holocaust anti-Semitism is no longer respectable. It was in the 1920s and 30s, but the Holocaust obviously changed that.
"But anti Zionism on the left is respectable and quite often that is used a cover." Mr Neil accepted that the far-right still represented a problem – particularly after incidents such as the recent events in Charlottesville, America.
He said: " I don't say for a moment that the far right is no longer a problem. We have seen the neo-Nazi nutters in Charlottesville in America.
"It is clearly a problem when the President of the US, the President of the greatest democracy in the world cannot bring himself to condemn these neo-Nazi nutters.
"That shames the United States - a country I love."
Mr Neil said the rise of conspiracy theories, often on social media, had allowed antisemitism to resurface. He also said the rise of authoritarian regimes across the globe represented a huge threat and described the failure of the Arab Spring as one of the great failures of modern times.
Praising the work of the Holocaust Educational Trust he said: "You might think the work of the Trust might have become less important - that we might have become more aware of the dangers of racism, of discrimination, of the need to for people to be treated properly. And yet I will argue with you tonight that it's now more important than ever. It is actually needed more than it has been before because of the scourge of antisemitism."