In an unexpected move last month, Britain's Crown Prosecution Service dropped charges against two British men who had denied passing politically sensitive information to a Chinese intelligence agent.
The CPS said the case was dropped because it needed evidence showing the UK considered China a threat to national security, but the government had not provided it after months of requests.
While the newly published documents detailed Chinese malign activity, they did not unequivocally state that China posed a threat to UK national security.
Starmer had earlier said the fault lay with the previous Conservative administration which was in power when the men were charged and which had only described Beijing as an "epoch-defining challenge".
The trial's collapse has led to accusations from opposition parties that the government was responsible because it did not want to jeopardise ties with China.
Seeking to draw a line under the issue on Wednesday, Starmer published witness statements by Britain's Deputy National Security Adviser Matthew Collins, which the prime minister said were made without involvement from ministers or political advisers.
In a document dated February 21, Collins said: "China and the UK both benefit from bilateral trade and investment, but China also presents the biggest state-based threat to the UK's economic security."
A statement dated August 4 contained a section on the government's assessment of the threat from China, including details of what he called the "active espionage threat that China posed to the UK".
A subsequent section in that document added: "It is important for me to emphasise, however, that the UK government is committed to pursuing a positive relationship with China to strengthen understanding, co-operation and stability.
Kemi Badenoch, the leader of the main opposition Conservative Party, had earlier told parliament: "This all stinks of a cover-up".
Starmer's office said he was told the case was in danger of collapsing a couple of days before it happened but that it would have been inappropriate to intervene.
A Conservative Party spokesperson responded to the release of the documents: "What has already been published shows the extent of the threat that China poses to the UK, and makes it all the more shocking that the prime minister knew of the imminent collapse of this trial, but did nothing to stop it."
The first witness statement from December 2023 said one of the men was allegedly passing on information to China about who was briefing former prime minister Rishi Sunak on China.
