The UK's spy agency MI5 has been formally told off by its own watchdog for lying about its relationship with a neo-Nazi informant. The watchdog — called the Investigatory Powers Commissioner's Office, or IPCO — published a 211-page report on July 16, 2026. The commissioner, Brian Leveson, said MI5 officers misled both the courts and the regulator about the informant, known as "agent X." He said their handling of the case "fell far below the standards the public, the courts and Ipco have every right to expect" The Guardian.

Agent X is a foreign national who was involved in neo-Nazi groups. MI5 recruited him as an informant before 2019, and he has since left the UK. During his time working with the security service, he used his informant status to threaten his girlfriend, identified as "Beth." He attacked her with a machete and tried to use his connection to MI5 to stop her from speaking out The Guardian.

Here is how the deception unfolded. MI5 had already told BBC reporter Daniel de Simone that agent X was an informant. But when the watchdog and the courts started asking questions, MI5 switched to a "neither confirm nor deny" stance — a common practice where agencies refuse to say anything at all about secret operations. De Simone had contacted agent X to say he planned to report that the man was "a dangerous neo-Nazi." Agent X immediately told MI5. Officers then tried to stop the BBC report by claiming agent X was "not a real extremist, but was pretending to be so at the behest of MI5" The Guardian.

The report traces a chain of internal failures. An officer identified as "Officer 2" had confirmed to the BBC that agent X was an informant. He later told his replacement, "Officer 3," that he "thought he had not" done so. Officer 3 then told colleagues the informant's status "had not been breached" — meaning the secret had not been revealed. That claim became the basis for MI5's position in a court case brought by Beth. The BBC published its report in May 2022 after winning a legal fight with the government. When the BBC's reporting corrected the record, MI5 had to retract its claims and apologise The Guardian.

MI5's Director General, Ken McCallum, apologised in February 2025 for giving courts incorrect information about the BBC's reporting on agent X Reuters. The IPCO investigation was launched under a formal order from the Prime Minister on January 1, 2026. It looked at whether MI5 gave false evidence to the High Court and to a special court called the Investigatory Powers Tribunal, which handles complaints about surveillance. IPCO gave a progress update to the Attorney General in October 2025 IPCO. According to the BBC, MI5 gave evidence based on lies to three courts while defending agent X BBC News. MI5 officers could now face prosecution for lying to the High Court The Telegraph.

Leveson was unusually blunt. "What makes this case particularly grave is that Ipco and the courts were misled," he wrote. "Failings of candour undermine the entire basis of oversight and accountability" The Guardian.

The broader context is that this is not just about one informant. The UK system for keeping spy agencies in check works on a simple idea: when the watchdog or a judge asks MI5 a question, MI5 tells the truth. It is like a building inspector trusting that a construction company will report its own safety problems honestly. If that trust breaks down, the whole system of checks and balances loses its foundation.

The agent X case is not the only time MI5 has been caught being less than forthcoming. A public inquiry into the 2017 Manchester Arena terrorist bombing, which killed 22 people, found that an MI5 witness initially did not give an accurate account of what the service knew about the suicide bomber. Two junior MI5 officers told the inquiry there had been intelligence that might have prevented the attack, which contradicted MI5's earlier position The Guardian.

The government has responded with new legislation. The Hillsborough law — named after the 1989 stadium disaster where police covered up their failures — was passed by the House of Commons in July 2026. It was amended to apply a "duty of candour" to individual MI5 officers. A duty of candour is a legal requirement to be honest and open. It has long applied to police forces in England and Wales. Extending it to MI5 officers means that, for the first time, individual staff can be held personally legally responsible for not telling the truth The Guardian.

In the past, when intelligence agencies failed to be honest, the usual response was an internal review, an apology, and promises to do better. The possibility that individual officers could now face criminal prosecution would be a significant shift. Whether prosecutors actually pursue charges based on IPCO's findings will show whether the oversight system Leveson describes can truly enforce its own rules.