One of the peculiarities of the ongoing row over anti-Semitism in the Labour Party – and perhaps its only benefit – is that it has introduced a whole new generation of progressives to some of the lesser-known episodes in the history of anti-Semitism.

Three years ago Ken Livingstone made the Haavara Agreement, a short-lived arrangement that enabled German Jews to escape to 1930s Mandate Palestine without losing all of their possessions, a topic of live debate in Labour Party meetings and on social media forums. Last year, Jeremy Corbyn’s apparent support for an anti-Semitic mural highlighted the conspiracy theory that Rothschild bankers sit at the heart of a New World Order that subjugates oppressed workers. And this week, it is the anti-Semitic writings of the radical nineteenth century intellectual J.A Hobson that Labour MPs are having to answer questions about in TV interviews.

This has come about because it emerged that Corbyn wrote the Foreword to a 2011 edition of Hobson’s Imperialism: A Study, without acknowledging the fact that Hobson’s theory of imperialism was shot through with anti-Semitism. In his influential study, Hobson wrote that the finance houses that propelled European imperialism were “controlled… chiefly by men of a single and peculiar race, who have behind them many centuries of financial experience” and “are in a unique position to manipulate the policy of nations”. In case anyone is in doubt regarding the identity of this “peculiar race”, Hobson then asserted that no “great war” could occur if “the House of Rothschild” did not want it to. “There is not a war, a revolution, an anarchist assassination, or any other public shock,” he went on, from which these “harpies” cannot “suck their gains”.

As an example of the anti-Semitic stereotype of Jewish financiers pulling the strings behind every calamity and getting rich from the suffering of others, it is hard to beat. Nor was this Hobson’s only anti-Semitic contribution. He also disliked the poor Jewish immigrants who had become increasingly numerous in the East End of London, because he believed the economic competition they brought was based on the same lack of morality that drove their wealthier co-religionists. Anthony Julius, in his comprehensive history of English anti-Semitism, described Hobson as the “most substantial” anti-Semitic polemicist of his time in this country.

Some people have defended Corbyn – and by implication Hobson – by pointing out that many others have praised Hobson’s theories on imperialism and his other writings, which should be taken on their merits. In other words, Hobson’s anti-Semitism was an unnecessary “mistake”, as one BBC documentary put it; an unfortunate occurrence that should not distract us from the value in his work.

This misses the point that anti-Semitism is, in its most developed form, a theory all of its own that claims the power to explain world events. It is no ordinary prejudice. Hobson’s anti-Semitic analysis of imperialism did not only rely on the claimed role of banks and financial houses that were actually owned by Jews. It fed off, and reflected, a much deeper cultural understanding, developed over centuries and lying deep in European Christian culture, in which money, property and the abstractions of finance were viewed as somehow having a “Jewish” character. As David Nirenberg wrote in his magisterial Anti-Judaism: The History of a Way of Thinking, “It is difficult to think of a financial innovation, practice, or crisis that was not discussed in terms of Judaism in the 19th and the early 20th centuries.”

This affected the left just as it did the right. Hobson’s views were derived largely from his belief that the Boer War was being fought on behalf of Jewish financiers, a view that was widespread on the British left at that time. In 1900 the Trades Union Congress passed a resolution claiming the war was being fought “to secure the gold fields of South Africa for cosmopolitan Jews, most of whom had no patriotism and no country”. Even the great Keir Hardie wrote in Labour Leader, the newspaper of his Independent Labour Party, that “modern imperialism is really run by half a dozen financial houses, many of them Jewish, to whom politics is a counter in the game of buying and selling securities”.

Left wing anti-Semitism has always existed in tension with the left’s commitment to anti-racism and has usually been the weaker of the two traditions – most people on the left, and in the Labour Party, are not anti-Semites. But it is an authentic left wing tradition nonetheless and its revival is what lies behind Labour’s current problems of anti-Semitism. Instead of claiming defensively that “only” 0.1 per cent of party members hold anti-Semitic views, Labour needs to recognise that the social media memes and Facebook posts about Zionist lobbyists and Rothschild bankers that populate the disciplinary cases they are failing to deal with effectively are a direct descendent of the radical anti-Semitism of Hobson and his contemporaries.

These ideas have not re-emerged in a political vacuum, but have taken root in the Labour Party precisely because they represent a pre-existing form of anti-Semitism that resonates in parts of the left. So far Corbyn has failed to recognise this or do enough to reverse it. With every episode like today’s, the belief will grow that the reason for his inaction is not ignorance, but because these attitudes sit within his own left wing tradition.

Dr Dave Rich is author of The Left’s Jewish Problem: Jeremy Corbyn, Israel and Antisemitism