Israel’s international isolation, triggered by revulsion over the large-scale illegal killing of Palestinian civilians in Gaza, will only deepen following new, detailed and credible allegations that leading politicians and intelligence agencies conspired – with help from Donald Trump’s administration – to spy on, undermine, “improperly influence” and threaten the work and officials of the international criminal court (ICC). Those allegedly targeted include the court’s former chief prosecutor, Fatou Bensouda, and the present incumbent, Karim Khan, possibly still the subject of covert operations. If so, this must cease immediately. Once again, the world is confronted by dismaying evidence that the state of Israel under the destructive leadership of its rightwing prime minister, Benjamin Netanyahu, has gone rogue. Once again, Netanyahu has crossed a line. Once again, his contempt for global opinion, for the values of the western democracies which too unquestioningly sustain and arm his country, and for the most basic principles of international law is on galling display. For all those who have previously supported Israel, and especially after Hamas’s appalling 7 October attacks, this is, once again, a deep disappointment. The allegations are the product of a joint investigation published this week by the Guardian, the Israeli-Palestinian publication +972 Magazine and the Hebrew-language outlet Local Call. They have been officially denied by the prime minister’s office as “false and unfounded” and intended to cause harm to Israel. But none of the specific claims has so far been addressed. That is now an urgent necessity. Netanyahu’s hard-right coalition already faced unprecedented diplomatic censure and criticism from friends and enemies alike. The UN security council and general assembly, the EU, Arab states, numerous aid agencies and even, belatedly, the Biden administration have all demanded a halt to its assault on Gaza, which Israel invaded after the October massacres of 1,200 people. All appeals have been flatly rejected by Netanyahu and his ultra-nationalist allies, whose militarily and politically unrealistic aim is to totally destroy Hamas. The latest result of this defiant, self-harming refusal to end the slaughter is the decision by Ireland, Spain and Norway to join a majority of countries in recognising Palestinian statehood. More pressure has come from the UN’s international court of justice (ICJ), which ordered Israel to halt its Rafah attacks, allow unrestricted aid supplies, and open Gaza to UN-led investigations. Yet the most dramatic recent development is from the ICC, with Khan’s decision to seek arrest warrants for Netanyahu and defence minister Yoav Gallant on charges of Gaza-related war crimes and crimes against humanity. This is exactly the outcome Israel’s leaders sought to avoid, and was, presumably, the prime motivation for their alleged subversion of the ICC. Their reaction has been furious. Netanyahu, prime minister for nearly all of the period in question, denounced the move as blatant antisemitism and urged all “civilised” countries to reject it. And veiled threats have been made against Khan. This latest crisis in Israel’s relationship with international justice – always fraught, given its long-established practice of ignoring UN security council resolutions relating to the post-1967 occupation – has been brewing since 2015. That was when Bensouda, Khan’s predecessor at the ICC, decided to examine possible crimes in the Palestinian territories committed by Israeli occupying forces and Palestinian groups. It is hardly surprising that Israel’s intelligence services, acting under political direction, interested themselves in the ICC’s activities. Naturally, they wanted to know what actions might ensue. But the Guardian’s investigation raises a key question: did Mossad, Shin Bet and agencies of the Israel Defense Forces (IDF) resort to improper, unlawful and, indeed, criminal means in their hunt for information? If the secret tapping and recording of Bensouda’s and other ICC officials’ phone and email conversations, alleged attempts to compromise her and smear her family, and personally threatening behaviour by a senior figure in Israeli intelligence constitute unlawful means – and reasonable people might conclude they do – then Netanyahu and his confederates have some very serious questions to answer. So, too, does Trump, who shares with Netanyahu the rare distinction of being a currently active national leader facing criminal charges. The investigation found that Israeli and Trump administration officials met in Washington in 2020 and allegedly discussed ways to thwart ICC inquiries into possible criminality both in Palestine and by US forces in Afghanistan. One apparent upshot was a decision by Trump to impose arbitrary sanctions on ICC officials, including Bensouda (which Joe Biden, his successor as president, has since rescinded). Following Khan’s decision to seek the arrest of Netanyahu and Gallant (as well as Hamas leaders), Trump has again gone on the attack while, shamefully, a group of Republican senators has told Khan they plan to target him personally if he pursues the matter. By attacking the ICC, Netanyahu, nothing if not predictable, has again confused his own personal interests with Israel’s by claiming the court poses a danger to the entire country. In sharp contrast, Bensouda and Khan have displayed courage and dignity in facing down overt and covert threats from some of the most prominent and unscrupulous actors on today’s international stage – including, for example, Russia’s Vladimir Putin, indicted last year over alleged war crimes in Ukraine. Having dared to do his duty and speak truth to power, Khan should be able to count on the firm support of all 124 state parties to the court. The fact that he cannot is a disgrace, particularly for Britain, which was instrumental in creating the ICC when Labour’s Robin Cook was foreign secretary. Rishi Sunak described Khan’s move against Netanyahu as “deeply unhelpful”. Biden called it “outrageous”. Putin and Xi Jinping in China, sworn enemies of the global rules-based order, must be laughing their socks off as they watch the democratic west pull itself apart over Israel’s outlaw behaviour. The onus is now on Netanyahu and his associates to show some respect for international opinion and common decency by answering, line by line, these well-founded allegations of an almost decade-long Israeli vendetta against the ICC. If they fail to do so, it’s probably because, in all truth, they cannot. Trump-like, they will double down on lies. Yet the world will know the truth, just as it has slowly come to know the truth of Gaza. The truth is, Israel under Netanyahu’s leadership, at a moment of truly dreadful national trauma, has gone rogue. It will not begin to heal until he, like the leaders of Hamas, is made to answer for his actions in a court of law. Simon Tisdall is the Observer’s foreign affairs commentator