The election of Keir Starmer as leader provides the Labour party with an opportunity to draw a line under its long-running controversy over antisemitism. But will this happen? Before Labour, or anyone else, can effectively address the problem they must rethink the way antisemitism operates in Britain today.

Conventionally, Labour’s friends and enemies say the party’s problem is the number of antisemites in its ranks. Partisans debate whether that number is large or small. Understandable though this is, the intense focus on antisemites has been a mistake. The more fundamental and widespread problem is one of antisemitism, not antisemites. The source of Labour’s difficulty lies in our political culture.

This relates to an unnoticed area of consensus in an otherwise bitter dispute. Unexpectedly, figures on opposite sides agree antisemitism should be conceived as a set of ideas that invade, contaminate and spoil a political body. Jeremy Corbyn and the chief rabbi, Ephraim Mirvis, agree antisemitism is “a poison; for Boris Johnson and Len McCluskey, it is a “virus”.

Why is antisemitism a problem for Labour when Conservative supporters are vulnerable to the same prejudice?

Words matter, and these metaphors lead us to misconceive the problem Labour faces and the sort of action the party needs to take. The notion that we are dealing with a virus or poison has led Labour to focus on individuals – antisemites who have “caught” the contagion. All sides call on Labour to suspend or expel these “bad apples” to fix the problem and make the barrel healthy again. But it is not as simple as that.

Let us consider the bigger picture. In Britain, the number of committed, ideological antisemites remains small: less than 5% of adults. In contrast, a large minority of the population, more than 30%, will readily agree with negative and stereotypical ideas about Jews: for example, that Jews get rich at the expense of others or that their interests are very different from those of non-Jews.

These negative ideas about Jews have accumulated over centuries and are embedded deeply within our culture. If we need a metaphor to comprehend antisemitism it is not “virus” but reservoir: a deep reservoir of stereotypes and narratives, replenished over time, and from which people can draw with ease, whether they intend to or not.

A significant minority of supporters of both main political parties assent to antisemitic stereotypes and prejudices drawn from this reservoir. This presents a puzzle. Why is antisemitism a problem for Labour when Conservative supporters are vulnerable to the same prejudice? The question we need to ask is not whether there is antisemitism in the Labour party but why the antisemitism that exists within Labour rises to the surface.

This does not happen because Labour members are more likely to be committed ideological antisemites. The reason can be found in the contingencies of political debate. At this time, Jews intersect, or are perceived to intersect, with some of the key issues Labour members care about: Israel and Palestine, and the operation of power within capitalist society. We see Labour members and supporters reaching for well-worn antisemitic ideas, stereotypes and narratives that provide a simplistic and, apparently, persuasive account of these issues.

Chief rabbi Ephraim Mirvis addresses a protest in Manchester against Jeremy Corbyn’s stance in 2018. Photograph: Christopher Thomond/The Guardian

Two misguided responses have followed from the pervasive misconception that Labour’s problem is a matter of individual antisemites and not the reservoir of antisemitism. The first has been denial. Defenders of the old leadership and party machine have been quick to emphasise the small number of “real” antisemites in the party. In many cases, Labour members accused of broadcasting antisemitic tropes have been defended on the basis of not being antisemites. Corbyn “does not have an antisemitic bone in his body”, a party spokesperson told the Jewish press in 2015, a phrase repeated often in the years that followed. When antisemitism is understood as only carried by fully fledged antisemites, insisting someone is not antisemitic serves to erase the problem.

On the other side of the debate, the problem has been seen as one of a host body afflicted with a sickness; Labour has been portrayed as a party riddled with antisemites, requiring radical surgical attention in the form of large-scale expulsions. Mainstream Jewish bodies have made increasingly sweeping demands to punish the offenders. Party leaders responded with assurances of a “zero-tolerance” approach, but struggled to implement it.

In the 2020 Labour leadership elections – to the anger of many in the party grassroots who maintain the denialist position – almost all candidates, including Starmer, followed the established pattern, asserting they would take a “zero-tolerance” approach to antisemitism and finally “eradicate” the problem. Yet the demand for zero tolerance is impossible to meet. Expulsion, though sometimes necessary, will never get to the heart of Labour’s problem. You can expel antisemites, but you cannot expel antisemitism. While antisemites might be rooted out, antisemitism, flowing through our political culture, almost certainly cannot be.

In the aftermath of the Corbyn leadership, there is an opportunity to escape this impasse. This requires us to take seriously the distinction between antisemites – thorough-going and often ideologically committed racists – and the more diffuse antisemitism that subsists in political culture. This is why education, even more than discipline, must be a priority for Labour. This should focus on fostering a deeper understanding of antisemitism as a form of racism, and on cultivating familiarity with its tropes and the harm done by them, regardless of intent.

Following on from this, political actors in the eye of the storm need to practise self-scrutiny rather than respond defensively. This approach has the potential to rebuild trust between political parties and British Jews.

Awareness of antisemitism as a reservoir, with some images and narratives persisting over time and others emerging anew, should also caution us to be aware of the range of sources of antisemitism. While Israel/Palestine was the context in which some leftwing activists turned to antisemitic discourse, the antisemitism in the Labour party also drew on long histories of anti-capitalist antisemitism, which in turn drew on Christian antisemitic themes, as well as on conspiratorial narratives. These themes have often gone overlooked in the battles over Zionism and anti-Zionism.

Similarly, an exclusive focus on the left leaves us unprepared to address the antisemitism that comes from elsewhere. In particular, from the political right, where it is surging globally, and could do so in Britain.

Political parties and movements need to develop the political language to speak to the crises to which antisemitism responds without creating openings for antisemitism. For example, a narrative of a “rigged economy” responds to the crisis of global capitalism but also opens a breach for discourses to flood in from the reservoir of antisemitism, while other anti-capitalist narratives do not.

Starmer’s election provides an opportunity to do things differently, but only if the problem is properly understood. We still have some way to go. This is a matter of political will and vision. Labour has a new leader. We will soon know whether the party can seize the moment.

• David Feldman is director of the Pears Institute for the Study of Antisemitism and a professor of history at Birkbeck, University of London. This piece was written in collaboration with Ben Gidley, a senior lecturer in psychosocial studies and affiliate researcher at the Pears Institute, and Brendan McGeever, a lecturer in the Department of Psychosocial Studies and affiliate lecturer at the Pears Institute. This article is based on a forthcoming essay in The Political Quarterly.