MI5 chief says China is a security threat to U.K. as officials trade blame over spy case collapse

Director General of MI5, the UK's Security Service, Ken McCallum, delivers the annual Director General's Speech at Thames House, in London on Thursday Oct. 16, 2025. (Jonathan Brady /PA via AP)

LONDON — China poses a daily threat to Britain’s security, the head of the country’s domestic intelligence agency said Thursday, remarks that step up pressure on authorities to explain why the prosecution of two men charged with spying for Beijing collapsed just before they were due to stand trial.

The government, prosecutors and opposition politicians, who were in power until last year, have traded blame over the failed criminal case as the United Kingdom tries to balance between challenging and engaging with the Asian superpower.

“Do Chinese state actors present a U.K. national security threat? The answer is of course yes they do, every day,” MI5 Director-General Ken McCallum told reporters during a rare public appearance. He said his agency had intervened to stop a threat from Beijing as recently as the past week.

McCallum said Beijing-backed meddling has included cyberespionage, stealing technology secrets and “efforts to interfere covertly in U.K. public life.”

China spying allegations

Academic Christopher Berry and parliamentary researcher Christopher Cash were charged last year with providing information or documents to China that could be “prejudicial to the safety or interests” of the U.K.

Then, last month, prosecutors dropped the charges.

Director of Public Prosecutions Stephen Parkinson pointed at the government, saying officials refused to testify under oath that China was a threat to national security at the time of the alleged offenses, between 2021 and 2023.

Prime Minister Keir Starmer denies interfering, and late Wednesday the government published witness statements submitted by Deputy National Security Adviser Matthew Collins describing China as “the biggest state-based threat to the U.K.’s economic security” and saying Beijing’s espionage activities “harm the interests and security of the U.K.”

McCallum called Britain’s relationship with China a “complex” mix of risk and opportunity, and said MI5 agents “detect and deal, robustly, with activity threatening U.K. national security.”

“Of course I am frustrated when opportunities to prosecute national security-threatening activity are not followed through for whatever reason,” he said, but added that prosecution decisions were out of MI5’s hands.

Cash and Berry were charged under the Official Secrets Act, a century-old statute that covers spying for countries deemed enemies of the U.K. It has since been replaced by new national security legislation.

The two men deny wrongdoing, and the Chinese Embassy on Thursday called the allegations “pure fabrication and malicious slander.”

“China never interferes in other countries’ internal affairs,” an embassy spokesperson said.

British intelligence authorities have ratcheted up warnings about Beijing’s covert activities, and Parliament’s Intelligence and Security Committee labeled Beijing a “strategic threat” in 2023.

Starmer’s center-left Labour Party government has tried cautiously to reset ties with Beijing after years of frosty relations over spying allegations, human rights concerns, China’s support for Russia in the Ukraine war and a crackdown on civil liberties in Hong Kong.

The spying controversy erupted as British officials consider China’s application to build a huge new embassy near the Tower of London that would be the biggest diplomatic complex in Europe. Critics say its scale and central location bring heightened risks of spying and sabotage.

On Thursday the government postponed the deadline for a final decision from Oct. 21 until Dec. 10.

Russia and Iran

In his annual speech outlining major threats to the U.K., McCallum painted a stark picture, saying the U.K. faces “multiple overlapping threats on an unprecedented scale” from both terror groups and states. He said China is one of the “big three” state threats, along with the more reckless Russia and Iran.

“State threats are escalating,” he said, with a 35% increase in the past year in the number of people MI5 is investigating for espionage.

He alleged that Russia and Iran are increasingly using “ugly methods,” including “surveillance sabotage, arson or physical violence.”

“Russia is committed to causing havoc and destruction,” he said. “In the last year, we and the police have disrupted a steady stream of surveillance plots with hostile intent aimed at individuals Russian leaders perceive as their enemies.”

He said Tehran is also plotting to injure and kill its enemies on British soil, with more than 20 “potentially lethal Iran-backed plots” disrupted in the past 12 months.

AI risks

The U.K.’s official terror threat level stands at “substantial,” meaning an attack is likely, and McCallum said MI5 has disrupted 19 late-stage attack plots since 2020.

He said attacks increasingly tend to come from small groups or individuals rather than broad networks, and suspects are getting younger, with one in five of those arrested last year under the age of 17.

Some plotters are motivated by al-Qaida and the Islamic State group – which are “once again becoming more ambitious” – and others by extreme right-wing ideology, he said. Still others reflect a messy stew of motivations bred in “squalid corners of the internet.”

The spy chief also said MI5 was looking at potential threats from out-of-control AI.

“Artificial intelligence may never ‘mean’ us harm,” he said. “But it would be reckless to ignore the potential for it to cause harm.”

Jill Lawless, The Associated Press