The head of the Crown Prosecution Service (CPS) has blamed the Government for the collapse of the Chinese spy trial in a damning letter.

Director of Public Prosecutions Stephen Parkinson said the CPS had spent “many months” attempting to secure witness statements which confirmed China was a threat to the UK.

Such statements were crucial in continuing an espionage case against Christopher Berry and Chris Cash.

However, the case collapsed on September 15 when barrister Tom Little KC told the Old Bailey: “We simply cannot continue to prosecute this case.”

Writing to MPs, Mr Parkinson said: “Notwithstanding the fact that further witness statements were provided, none of these stated that at the time of the offence China represented a threat to national security, and by late August 2025 it was realised that this evidence would not be forthcoming.”

A fierce political row has followed the letter, with the Prime Minister insisting that the former Conservative Government was to blame as it did not formally label Beijing a threat – while Labour was unable to do so retrospectively.

Mr Parkinson had previously blamed an “evidential failure” for the collapse of the trial, but at the time gave no further explanation.

Now, he has referenced a previous High Court ruling in a separate Russian spy case from last year.

That ruling found that to be classified as an “enemy” under the 1911 Official Secrets Act, a country, at the time of the alleged offence, must have posed a real threat to the national security of the UK.

Mr Parkinson said that prosecutors sought evidence from the Government following this ruling, but no witnesses would confirm that China met the requirements to be classified as an enemy.

Mr Cash, a former head of a China policy group, and Mr Berry were charged in April 2024 under the Official Secrets Act.

They were accused of collecting and passing on information which could have aided an enemy.

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Both men have denied the allegations.

Sir Keir Starmer confirmed that he had been briefed throughout the process, but argued that because the Tories were in power at the time of the alleged offence and had not classified China as a threat, Labour was unable to apply the law retroactively.

The Prime Minister said: “Let me just be really clear about this.

“What matters is what the designation was in 2023, because that’s when the offence was committed and that’s when the relevant period was.

“Therefore, statements were drawn up at the time according to the then government policy, and they haven’t been changed in relation to it, that was the position then.

“You can’t prosecute someone two years later in relation to a designation that wasn’t in place at the time.”

Alicia Kearns, the Conservative MP who formerly employed Mr Cash, had previously said the withdrawal of a witness prompted “serious questions about constitutional impropriety”.

She said: “In the public interest, the Government must disclose ministerial involvement, and come clean on whether any Government witnesses were withdrawn.

“Mr Starmer must answer: was it no longer in the public’s interest to prosecute, or more likely he and his Labour Government don’t have the mettle to defend the British people and our great democracy?”