Downing Street has insisted the decision to drop charges was made by the CPS, with no minister, member of the government or special adviser involved.
The government has maintained that it is frustrated the trial collapsed.
Prime Minister Sir Keir Starmer has also sought to shift the focus to the previous Conservative government, which was in power when the alleged offences took place.
He argued the prosecution could only be based on the Tory government’s position at that time, when he says China was not designated a “threat to national security”.
Current Conservative leader Kemi Badenoch has rejected this, pointing to examples where Tory ministers and government documents had described China as a “threat”.
A number of former senior security and legal officials have also questioned the government’s argument.
The Tories have accused the government of refusing to give the CPS the evidence it needed to secure convictions.
They have suggested that the PM’s national security adviser Jonathan Powell, who has sought closer relations with Beijing, may have intervened.
The government has insisted Mr Powell, who is one of the PM’s most senior advisers and political allies, was not involved in any decisions about the evidence provided in the case.
It says deputy national security adviser Matthew Collins, a civil servant, provided witness statements for the government under both the Tories and Labour.
Security Minister Dan Jarvis told MPs Mr Collins was given “full freedom to provide evidence without interference” from ministers and special advisers, and that his evidence did not “materially change”.
