For months, the Royal Commission into Anti-Semitism and Social Cohesion has heard evidence about how anti-Semitism has changed in Australia.

Old prejudices have acquired new language. Criticism of Israel has nothing to do with anti-Semitism. But “Zionist” is increasingly used as a substitute for “Jew”. Conspiracy theories about Jewish power are repackaged as claims about “Zionist” influence. And when Jewish Australians object, their concerns are too often dismissed as attempts to silence criticism of Israel.

Last week, we saw that pattern play out on the floor of the Australian Senate.

Greens Senator Nick McKim accused the Labor Government of being “captured by Zionist interests”. When Senator James Paterson challenged him, McKim told Paterson that he was “captured by Zionist interests” too. He later withdrew the personal remark, but insisted he was entitled to use the broader formulation.

I wrote to Senator McKim afterwards and asked him to reflect on what he had said.

The allegation that Jews exercise excessive or hidden influence over governments is one of the oldest forms of anti-Semitism. It portrays Jews not as fellow citizens with views and interests like everyone else, but as a powerful and suspect group manipulating institutions from behind the scenes. For generations, that idea has helped justify exclusion, persecution and violence.

The allegation is also difficult to reconcile with observable reality. The relationship between the Australian Government and major Jewish communal organisations has been significantly strained since 7 October, including over a series of foreign policy decisions strongly opposed by those organisations. Whatever view one takes of those disputes, they hardly suggest a Government under the control of some undefined Zionist force. But conspiracy theories do not depend on evidence. Their power lies in identifying a group to distrust and blame.

In his response, Senator McKim said that not all Jews are Zionists and not all Zionists are Jews. Of course he is correct.

But then who are the “Zionist interests” that he says have “captured” the Government?

Are they different from the “Jewish lobby and the Zionist lobby” that his Greens colleague Jenny Leong once said used their “tentacles” to reach into areas of power and influence? Leong later apologised and acknowledged the anti-Semitic implications of her language. McKim has doubled down.

For the overwhelming majority of Australian Jews, Israel and Zionism, the belief in Jewish self-determination in the Jewish people’s ancestral homeland, are deeply intertwined with Jewish identity. The question is not whether “Zionist” and “Jew” are interchangeable. They are not. The question is whether “Zionist” is being used as a proxy for “Jew”, allowing an old prejudice to be repackaged as legitimate political discourse.

Bondi provided the most horrific illustration of why that matters. The alleged perpetrators condemned “Zionists” as they explained the motivation for their attack, and then opened fire on a Jewish Chanukah celebration.

The royal commission has heard versions of the same phenomenon in different settings. Jewish Australians have described being labelled “Zionists” and then excluded, intimidated or vilified. Meta told the commission that it had changed its hate speech rules after identifying cases in which “Zionist” was being used as a proxy for Jews in conspiracy theories about control of governments and the media.

None of this means that criticism of Zionism or Israel is inherently anti-Semitic. It plainly is not. But that was never the issue here.

McKim was not criticising an Israeli Government decision. He was not criticising an Australian policy towards Israel. He was not identifying a Zionist organisation and scrutinising its lobbying. He alleged that unidentified “Zionist interests” had captured the Australian Government.

Yet his response to me declared that “criticism of Israel is not anti-Semitic”, accused me of trying to suppress legitimate political debate and concluded by declaring that Israel was committing genocide in Gaza. That is not an answer to the objection. It is a sleight of hand that turns my challenge to the anti-Semitic insinuations of his rhetoric into an entirely unrelated argument about Israel.

This matters not only because of what one senator said. Repeated often enough, language about hidden “Zionist” influence shifts the boundaries of acceptable discourse. Claims that should immediately cause alarm become part of ordinary political debate and give others permission to repeat them.

Yet, so far, no Government minister has publicly condemned the substance of McKim’s remarks.

The Government understands this principle. Last year, Anthony Albanese described Greens leader Larissa Waters’ response to the Manchester synagogue attack as “undignified” and “not worthy of a senator”. Weeks later, Penny Wong moved to censure and suspend Pauline Hanson after her burqa stunt, condemning conduct that mocked and vilified an entire faith. The incidents are different, but the principle is not. Fighting prejudice cannot depend on which minority is targeted or which political party is responsible.

McKim was given an opportunity to reflect. Instead, while a royal commission is examining contemporary anti-Semitism and its impact on Australian social cohesion, he repeated the allegation that the Government had been “captured by Zionist interests”.

We should not need to await the commission’s final report to understand why that matters. Political leaders have a responsibility to draw boundaries around what we are prepared to accept in Australian public life. The Government should say so. And Parliament should be where that standard is set, not where the boundary is eroded.

Jeremy Leibler is president of the Zionist Federation of Australia