A year ago, it was highly controversial to claim – even for a genocide scholar, and an Israeli one at that – that Israel was committing a genocide in Gaza. Today, it is becoming controversial to deny it.

Terms such as “genocide”, foreign secretary David Lammy said in the Commons on Monday, in response to a question from Theresa May’s former aide and now Tory MP Nick Timothy, “are quite properly, legal terms that must be determined by international courts”.

That didn’t prevent Lammy, a former barrister, from making an off-the-cuff assessment about the applicability of the term to Israel: “Those terms were largely used when millions of people lost their lives in crises like Rwanda, the second world war and the Holocaust, and the way that they are used now undermines the seriousness of that term.” By this logic, Lammy may himself have undermined the seriousness of the term when he used it in reference to the Uyghurs, Rohinghas and Bosnian Muslims (Lammy attended a parliamentary reception to commemorate the Srebrenica genocide in 2022). On Wednesday, Keir Starmer backed up Lammy, boasting that “I have never described what is going on in Gaza as genocide”.

While a few months ago Lammy’s genocide denial may have gone unnoticed, this week they drew condemnation from his parliamentary colleagues, including a letter from Scottish National party MP Chris Law demanding he correct his contention that “genocide” was only applicable “where ‘millions of people’ have been killed”. The International Centre for Justice for Palestinians also strongly criticised Lammy’s denial of the Gaza genocide. This widespread blowback is a reflection of the growing international consensus – and how out-of-step western governments are with their own populaces.

71% of the 2,980 UK adults polled by Find Out Now for the UK Palestine Affairs Network in June felt it was fair to label Israel’s actions in Gaza a genocide. And despite being from one of the most institutionally pro-Israel nations on Earth – bankrolling Israel’s offensive in Gaza to the tune of $22.76bn (£17.5bn) – 56% of US Democrats believe Israel is committing a genocide, according to an April poll of 1,265 Democratic voters conducted by Zeteo and Data For Progress.

The popular belief that Israel is committing a genocide has been produced in part by a barrage of social media evidence, one underpinned by a growing body of investigative reporting and scholarship. On Friday, Forensic Architecture – a UK-based organisation led by British Israeli Eyal Weizman that uses architectural techniques to expose global human rights abuses – produced an 827-page report on Israel’s actions in Gaza since October 2023. Using spatial analysis of the strip’s civilian infrastructure, the report – one of the most thoroughgoing of its kind – reveals “the near-total destruction of civilian life in Gaza”.

The report concludes that the evidence “indicate[s] a systematic and organised campaign to destroy life, conditions necessary for life, and life-sustaining infrastructure.” It is this systematic approach that leads Weizman and his team to conclude that Israel is not permitting massive collateral damage in a military campaign against Hamas, but is perpetrating a genocide.

Forensic Architecture adopts its understanding of the term genocide from Raphael Lemkin, the Polish Jewish lawyer who lost 49 family members in the Holocaust and coined the term genocide in 1944. A genocide, according to Lemkin, is a “coordinated plan of different actions aiming at the destruction of essential foundations of the life of national groups, with the aim of annihilating the groups themselves” (the United Nations based its own definition of genocide – ratified in its genocide convention of 1948 – on Lemkin’s).

Lemkin was insistent that numbers – the “millions” referred to by Lammy – were not the only or even the primary measure of genocide, one of whose signature features was the attempted eradication of a group’s identity and culture. In April, a panel of 24 UN experts announced its view that Israel was committing “scholasticide” through the deliberate targeting of Gaza’s educational infrastructure (Israel has damaged or destroyed 80% of Gazan schools and targeted all 12 of its universities). The Lemkin Institute for Genocide Prevention, established in 2021 to improve the public understanding of genocide, declared Israel’s actions tantamount to genocide in late May.

Meanwhile, the facts on the ground have gradually convinced several of those initially sceptical of the term – including Israeli academics – to use it.

“As a historian of genocide, I believe that there is no proof that genocide is now taking place in Gaza,” wrote the Israeli American historian Omer Bartov in the New York Times on 10 November 2023, though warning there was “potential” for a genocide to take place. 11 months later, Bartov wrote: “I no longer believe that.”

Reflecting on his experiences in Israel for the Guardian on 12 August, Bartov wrote: “By the time I travelled to Israel [to deliver a lecture on 19 June 2024], I had become convinced that at least since the attack by the IDF on Rafah on 6 May 2024, it was no longer possible to deny that Israel was engaged in systematic war crimes, crimes against humanity and genocidal actions.” (The Guardian has gradually permitted the term genocide into its lexicon, though editor-in-chief Katharine Viner retains an informal prohibition on using the term as an assumed fact).

Similarly, while in March the UN special rapporteur on the occupied Palestinian territories Francesca Albanese concluded there were “reasonable grounds” to conclude that Israel was committing a genocide, her latest report for the UN goes much further. Entitled “Genocide as colonial erasure”, the report concludes that “since the previous report of the special rapporteur, and despite the ICJ [International Court of Justice] interventions, genocidal acts have proliferated”.

Among historians, journalists, international observers and ordinary people, describing Israel’s actions in Gaza as a genocide has gone from a contentious claim to a generally accepted fact. Among UK politicians, however, the term remains unsayable. While this may once have appeared prudent, it increasingly appears foolish.