Sir Keir Starmer has said no ministers were involved in the collapse of the trial of alleged Chinese spies.
The Prime Minister reiterated that responsibility lay with the previous Conservative administration which was in power at the time of the alleged offences.
It came after two former top civil servants questioned his explanation for the pulling of the prosecution of Christopher Cash, a former parliamentary researcher, and Christopher Berry, a teacher.
Sir Keir has maintained that because the last Tory administration had not designated China as a threat to national security, his Government could not provide evidence to that effect, which the director of public prosecutions Stephen Parkinson said was required to meet the threshold for prosecution.
Mr Parkinson had blamed ministers for failing to provide the crucial evidence needed to proceed.
Former cabinet secretary Lord Simon Case said intelligence chiefs had warned of the threat from China for years, while his predecessor Lord Mark Sedwill expressed puzzlement about why the trial fell apart because Beijing was âof courseâ a threat to the UK.
But Sir Keir argued that the evidence should focus on the stated foreign policy position towards China of the Tory administration in place between December 2021 and February 2023, when the alleged offences occurred â which was not to call President Xi Jinpingâs country a threat.
In the 2023 refresh of the integrated review of defence, published under Rishi Sunakâs premiership and one month before the two menâs arrest, the Asian superpower was described as an âepoch-defining challengeâ, but not as a threat.
Sir Keir was asked at a press conference during a trade trip to India whether any minister was involved in the decision not to provide the Crown Prosecution Service (CPS) with evidence that, at the time of the alleged offences, China represented a threat to national security.
The Prime Minister, a former director of public prosecutions, said: âThe evidence in this case was drawn up at the time and reflected the position as it was at the time. And that has remained the situation from start to finish.
âThat is inevitably the case, because in the United Kingdom you can only try people on the basis of the situation as it was at the time.
âYou canât try people on the basis of situation as it now is or might be in the future. And therefore, the only evidence that a court would ever admit on this would be evidence of what the situation was at the time.
âSo thatâs the base on which the evidence was drawn up, the witness statements were drawn up. And I can be absolutely clear, no ministers were involved in any of the decisions since this Governmentâs been in in relation to the evidence thatâs put before the court on this issue.
âThe evidence was the evidence as it then was, thatâs the only relevant evidence, and that evidence was the situation as it was under the last government, the Tory government, rather than under this Government.
âItâs not a party political point. Itâs a matter of law. You can only try someone on the basis of the situation as it was at the time of the alleged offence.
âYou canât try them on the basis of the situation as it might evolve, weeks, months, years down the line. Thatâs a fundamental and thatâs at the centre of this particular issue.â
Mr Cash and Mr Berry were charged by the CPS in April last year with the offence of spying under the Official Secrets Act 1911 after they were accused of collecting and communicating information which could be âuseful to an enemyâ.
The case against the two men â who both denied charges â was dropped on September 15.
Mr Parkinson said the CPS had tried âover many monthsâ to get the evidence it needed to show China was a threat to national security, but it had not been forthcoming from Sir Keirâs administration.
Critics have pointed to Sir Keirâs attempts to build relations with the worldâs second-biggest economy as a possible reason for the Governmentâs reluctance to label China an âenemyâ or threat.
