MI5 boss says he will 'never back off' from China threat - as Beijing plot disrupted in last week

The head of MI5 says he will "never back off" from confronting threats from China as he revealed his officers disrupted a case linked to Beijing in just the past week.

More broadly, Sir Ken McCallum said the number of people in the UK under investigation for "state threat activity" - also including from Russia and Iran - has jumped by 35% in the past year compared with the previous 12 months.

He admitted he felt frustration at the collapse last month of a trial against two British men accused of spying for China, but he stressed that the Security Service had still successfully derailed the alleged espionage operation.

With pressure mounting on Sir Keir Starmer over why the high-profile trial foundered, the director general of MI5 - choosing his words carefully given the controversy - confirmed that "Chinese state actors" pose a threat to UK national security "every day".

Politics latest: Senior MPs launch 'formal inquiry' into China spy case collapse

He also warned that the wider threat from nation states is escalating and becoming as ugly as terrorism.

He used an annual speech at MI5's headquarters in London to say:

• Attempts by states - principally China, Russia and Iran - to carry out operations involving violence, sabotage, arson or surveillance are "routinely" being uncovered

• MI5 has tracked more than 20 "potentially lethal" plots backed by Iran in the past year

• Russia is hatching a "steady stream" of surveillance plots with "hostile intent", while MI5 officers take it as a working assumption that Russian trolls will attempt to exploit any particular "fissures" in UK society using online posts, though these efforts are largely unsuccessful

• On terrorism, MI5 and the police have disrupted 19 late-stage attack plots since 2020 and have intervened in many hundreds of developing threats

• There is growing concern about children becoming involved in terrorism, with one in five of the 232 terrorism arrests last year involving minors under 17

"MI5 is contending with more volume and more variety of threat from terrorists and state actors than I've ever seen," Sir Ken said.

Declaring a "new era", the MI5 boss warned of "fast-rising" state threats coupled with a "near record" number of terrorism investigations.

He said this was forcing the biggest shift in MI5's mission since the 11 September 2001 terrorist attacks on the United States.

China is a particular challenge as the Starmer government seeks to bolster economic ties with Beijing, while also wary of the security threat posed by Chinese spies.

"The UK-China relationship is by its nature complex, but MI5's role is not," Sir Ken said.

"We detect and deal, robustly, with activity threatening UK national security."

These threats range from cyber espionage; attempts to steal secrets from universities such as by cultivating academics; or efforts to target parliament and other parts of public life.

"MI5 will keep doing what the public would expect of us, preventing, detecting and disrupting activity of national security concern," said the MI5 chief.

"Our track record is strong. We've intervened operationally again just in the last week and we will keep doing so."

The spy boss continued: "I am MI5 born and bred. I will never back off from confronting threats to the UK wherever they come."

The speech was delivered amid a growing row around a decision by Crown Prosecution Service (CPS) to drop the espionage trial of Christopher Cash, a former parliamentary researcher to two prominent Conservative MPs, and Christopher Berry, a teacher.

Both have denied any wrongdoing.

Read more: Three questions about spy case that need answering

Prosecutors said the government had not provided evidence that China represented a threat to national security, prompting allegations by the Conservatives that the prime minister's team had interfered with the case to protect the UK's trading ties with China.

Attempting to push back, ministers on Wednesday released written evidence by Matthew Collins, the deputy national security adviser, that was given to the CPS. It spelt out the threat posed by China and his assessment of the allegations against the two individuals.

Given the political storm, the MI5 director general was careful when responding to questions on the furore.

But he chose to voice his support for Mr Collins who he has worked with, describing him as a "man of high integrity and a professional of considerable quality".

Sir Ken was asked by journalists if he had been frustrated at the failure to prosecute.

"Of course I am frustrated when opportunities to prosecute national security threatening activity are not followed through for whatever reason," he said, though he noted not all cases that involve MI5 lead to prosecution.

"I would remind you all that in the particular case… the activity was disrupted."

On whether he regarded China to be a threat, the MI5 chief said: "Do Chinese state actors present a UK national security threat? And the answer is of course yes they do every day."

But he added that UK wider bilateral foreign policy on China is a matter for the government.

Sky News has approached the Chinese embassy for comment.

(c) Sky News 2025: MI5 boss says he will 'never back off' from China threat - as Beijing plot disrupted in last wee