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. 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”.

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 UK.