China presents a daily threat to UK security, MI5 chief says after spy case collapse

China poses a daily threat to Britain’s security, the head of the country's domestic intelligence agency said on 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, opposition politicians and prosecutors 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 UK 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 on Thursday.

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 UK public life."

Allegations of spying for China

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 UK.

Then, last month, prosecutors said the charges were being dropped.

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

UK Prime Minister Keir Starmer denies interfering, and late on Wednesday the government published witness statements submitted to court by Deputy National Security Advisor Matthew Collins describing China as "the biggest state-based threat to the UK’s economic security".

Bejing's espionage activities "harm the interests and security of the UK," he said.

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 UK national security."

"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.

British intelligence authorities have ratcheted up their warnings about Beijing's covert activities and parliament’s Intelligence and Security Committee labelled Beijing a "strategic threat" in 2023.

The centre-left Labour Party government, which took power last year, has tried cautiously to reset ties with Beijing after years of frosty relations over spying allegations, human rights concerns, China’s support for Russia's full-scale invasion of Ukraine and a crackdown on civil liberties in Hong Kong, a former British colony.

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 It has since been replaced by new national security legislation.

The two men deny wrongdoing and the Chinese Embassy has called the allegations fabricated, dismissing them as "malicious slander".

Threats from Russia and Iran

McCallum also painted a stark picture, saying the UK faces "multiple overlapping threats on an unprecedented scale" from both terror groups and states.

He said China is one of the "big three" countries behind the 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, "including against our Parliament, our universities, our critical infrastructure."

He said Russia and Iran are increasingly using "ugly methods," including "surveillance sabotage, arson or physical violence," something he said he had not previously seen from nations during his intelligence career.

"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.