The China spying row has revealed disturbing weaknesses in the processes of the UK state. It cannot be in the national interest for a case involving national security to get so close to the courts and then for it to be abandoned in what remain mysterious circumstances. Public confidence, as well as security itself, are inevitably placed at risk. But this genuinely important issue now risks being blanketed by the fog of the party-political battle at Westminster.

For the third time this week, MPs spent Thursday trading accusations about whether the Conservatives or Labour are more to blame for the fiasco of last month’s collapsed prosecution. To be fair, the latest exchanges did not descend to the abject “did-didn’t” level that was reached at prime minister’s questions on Wednesday. Politicians from Sir Keir Starmer down are fond of saying that the national interest comes before the party interest. But there has been too little evidence of that principle in the current dispute.

The main issue is not, in fact, whether China is a security threat to the UK. That is a no-brainer. Many countries, including Britain, spy on their foes – and perhaps on some of their friends too. But the threat posed by China reflects its size, wealth and values. Delivering his annual threat update on Thursday, the head of MI5, Sir Ken McCallum, said that he encountered that threat on a daily basis. “Do Chinese state actors present a UK national security threat?” he asked. “The answer is, of course, yes.”

What is in doubt is whether the processes of the British state are as well honed as they should be to cope with such cases in modern circumstances. The collapse of an alleged spying case involving one of the three countries identified by Sir Ken as the chief threats to the UK – Iran and Russia are the others – provides its own answer. Very obviously, this was a case of state failure.

The governance problem is on two levels. The first is that the law has not kept pace. The two defendants (who denied any wrongoing) were charged and faced trial under the Official Secrets Act 1911, which was still in force when they were first arrested. Yet the security world of 2025 is radically different from that of 1911. Hence the changes brought in by the National Security Act in 2023. Hence, also, the pressure at a late stage to strengthen the witness statements by civil servants that were published this week. But the law should, and could, have been reformed years ago.

The second problem is with decisions to prosecute in national security cases. This necessarily involves a sensitive balance between the government, as the primary custodian of the national interest, and the independent Crown Prosecution Service, headed by the director of public prosecutions. Ministers insist that, like the head of MI5, they wanted the China trial to go ahead. But the collapse of the case suggests that this government and these law officers have got that balance wrong. That must change.

Fairly or unfairly, the China case collapse damages trust. It makes Sir Keir’s government look hesitant where national security is concerned. Labour’s struggle to get its story straight has not helped. This even has distant echoes of the very first Labour government, which fell after Ramsay Macdonald’s decision not to proceed with the Campbell incitement to mutiny case in 1924. Labour now has a big majority, while Mr Macdonald had none at all, but Sir Keir should not underestimate the stakes.