The head of Britain’s domestic intelligence agency, MI5 Director-General Ken McCallum, warned Thursday that China poses a “daily” threat to the United Kingdom’s national security, underscoring mounting tensions after the collapse of a high-profile spy case.

Speaking at a rare press briefing, McCallum said MI5 had thwarted a recent Beijing-linked threat and accused Chinese state actors of cyberespionage, tech theft, and covert interference in British public life. “Do Chinese state actors present a U.K. national security threat? The answer is yes — every day,” he said.

The comments came days after prosecutors abruptly dropped charges against two men — academic Christopher Berry and parliamentary researcher Christopher Cash — accused of spying for China between 2021 and 2023. The move sparked political backlash, with officials and prosecutors blaming each other for the failure.

Director of Public Prosecutions Stephen Parkinson said the case collapsed because the government refused to confirm under oath that China was considered a national security threat during the alleged offenses. Prime Minister Keir Starmer denied interference, later releasing testimony from Deputy National Security Advisor Matthew Collins, who described China as “the biggest state-based threat to the U.K.’s economic security.”

McCallum said he was “frustrated” that prosecutions weren’t pursued, though decisions lay beyond MI5’s control. The intelligence chief added that Britain’s relationship with China remains a “complex mix of risk and opportunity.”

Beyond Beijing, McCallum warned that Russia and Iran also pose “overlapping threats” to Britain. He said MI5 had disrupted a wave of espionage and violent plots over the past year, including 20 Iran-backed assassination attempts on British soil and Russian-led sabotage efforts.

“State threats are escalating,” McCallum said. “We face multiple adversaries using increasingly aggressive methods.”