The Conservatives have submitted an urgent question in Parliament, asking ministers to address MPs on Monday to explain why the trial collapsed.
Shadow home secretary Chris Philp told the BBC ministers “must urgently explain why it chose not to disclose the reams of information it has demonstrating China was a threat to national security in the 2021-2023 period”.
He said: “It looks as if Jonathan Powell was behind this decision – and he should resign if he is.”
Meanwhile, several former Conservative ministers and advisers have told the BBC there was no official designation of whether a country amounts to a threat.
They claim there is a document with “hundreds” of examples of Chinese activity posing a threat to the UK at the time of the alleged offences, which could have been given as evidence.
Sources cited the hack on the Ministry of Defence, which ministers suspected China was behind, as one of many incidents.
“I don’t think there is a sane jury in the world that would look at that evidence and conclude China was not a threat,” a source in the last government said.
Former Conservative ministers also point to public statements, including from the former head of MI5 Ken McCallum, who in 2023 said there had been a “sustained campaign” of Chinese espionage on a “pretty epic scale”.
The Liberal Democrats said the government’s approach to China was “putting our national security at risk”.
The party urged the government to block the planning application for a new Chinese embassy in London.
“Giving the green light to the super embassy being built in the heart of the City of London and above critical data connections would enable Chinese espionage on an industrial scale,” Liberal Democrat foreign affairs spokesman Calum Miller said.
Mr Cash, a former parliamentary researcher, and Mr Berry, were charged under the Official Secrets Act in April 2024, when the Conservatives were in power.
They were accused of gathering and providing information prejudicial to the safety and interests of the state between December 2021 and February 2023.
Under the Official Secrets Act, anyone accused of spying can only be prosecuted if the information they passed on was useful to an enemy.
Last month, the DPP said “the case could no longer proceed to trial since the evidence no longer met the evidential test”.
Additional reporting by Maia Davies
