Britain’s top intelligence officer has revealed MI5 thwarted an attack from China within the past week, as he issued a stark warning that Beijing presents a “daily” threat to the UK’s national security.

In a rare and extraordinary public intervention, MI5 Director-General Sir Ken McCallum said the agency had disrupted a major China-linked operation “in the interest of the UK’s national security” just days ago.

The revelation came amid deepening political fallout from the collapse of a major spy trial involving two men accused of spying for China — a case McCallum said left him “frustrated” after it was dropped before reaching court.

Speaking at MI5’s London headquarters, McCallum described China’s actions as a multi-layered campaign of “cyber-espionage,” “clandestine technology transfer,” and attempts to “interfere covertly in UK public life,” including intimidation of pro-democracy activists.

“The UK–China relationship is, by its nature, complex, but MI5’s role is not: we detect and deal, robustly, with activity threatening national security,” he said.
“When it comes to China, the UK needs to defend itself resolutely against threats and seize the opportunities that demonstrably serve our nation.”

His comments come as Housing Secretary Steve Reed delayed a decision on whether to approve a new Chinese “super-embassy” near the Tower of London, a project critics claim could become a major espionage hub for Beijing.

The timing has further embarrassed the government, already under pressure to explain the abrupt collapse of the spying case against Christopher Cash and Christopher Berry, who were accused of passing sensitive material to Chinese intelligence. Both deny wrongdoing.

Government documents released on Wednesday revealed that Deputy National Security Adviser Matt Collins had described Chinese intelligence services as “highly capable,” warning they conduct “large-scale espionage operations” that threaten Britain’s economic resilience and democratic integrity. Despite this, the Crown Prosecution Service unexpectedly dropped the charges, prompting a formal parliamentary inquiry into the case’s failure.

The revelation has triggered political infighting. Critics accuse Prime Minister Keir Starmer’s government of being too cautious in labeling China a national security threat. Conservatives argue Labour has prioritized economic ties over security vigilance.

Starmer’s spokesman defended the government’s position, saying it would have been “absurd” for the Prime Minister to intervene in a live case, while the Labour leader insisted his officials “did everything possible” within “constraints imposed by the previous government’s position on China.”

Meanwhile, Ben Bland, director of the Asia-Pacific Programme at Chatham House, cautioned against letting the scandal dominate the wider relationship with Beijing. “Espionage is one thing, but the challenge from China is much bigger than any one case,” he told The Independent.

Hours after McCallum’s remarks, the Joint Committee on the National Security Strategy announced a formal inquiry into the collapsed case, with chair Matt Western warning that “many questions remain unanswered.”

As the debate deepens, McCallum’s intervention — confirming an active China-linked plot was stopped within days — underscores both the immediacy of the threat and the rising tension between intelligence imperatives and political diplomacy.

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