Labour MPs warned a government minister today that they will pursue him relentlessly unless he ends the "conspiracy of silence" over the Shrewsbury pickets.
Justice Minister Jeremy Wright incurred MPs' wrath for dishing up evasive answers to parliamentary questions on the cover-up surrounding the conviction of 24 pickets under ancient laws 40 years ago.
Parliamentary terriers Tom Watson and Grahame Morris pledged to give ministers no peace until they publish all the secret government documents on the case.
Mr Watson declared: "I am not going to let this drop. There will be a relentless parliamentary scrutiny until the truth comes out."
Fellow Labour MP Mr Morris protested: "What we are faced with is a clandestine conspiracy to cover up the role of top politicians and the security service in these unjust convictions."
The minister claimed the "majority" of papers relating to the Shrewsbury 24 trials were already available at the Kew National Archives.
But then he said that he could not say how many secret files existed because the government "does not hold a single list of files or records on this subject."
He claimed that the Cabinet Office had retained "a small number of papers supplied by or otherwise relating to the intelligence agencies."
Adopting classic Whitehall newspeak Mr Wright added: "To provide details of the national security risks that might be posed by the release of this information would itself be detrimental to the purposes the exemption is designed to protect."
He said Justice Secretary Chris Grayling had viewed secret Cabinet Office papers to "satisfy himself" that they fell within the rules governing retention of security and intelligence material.