Royle Family actor Ricky Tomlinson today accused the Government of deliberately preventing names from being added to an e-petition calling for the release of official papers relating to the jailing of pickets over 40 years ago.
The 74-year-old was one of the so-called Shrewsbury 24, who were sent to prison on conspiracy charges after a building workers strike over pay and conditions in 1972.
Campaigners want documents from Cabinet meetings and the secret services to be released to prove their belief that the charges were politically motivated.
An early day motion has been tabled in the Commons calling for the documents to be published, and an e-petition was launched in a bid to gather the 100,000 names needed to trigger a debate in Parliament.
Mr Tomlinson told Unison's national conference in Liverpool that the e-petition had attracted tens of thousands of hits, but 42,000 had been "debarred" because people had not signed it properly.
He blamed Downing Street for the discrepancy, telling delegates that a paper petition had now been launched to gather the necessary number of names.
"We already have 30,000 names and we will reach 100,000, then we will march on Downing Street and demand justice.
"What happened to us was disgraceful. We know our telephones were tapped, names were put on a blacklist and people never worked again."
The actor said leaders of the country's biggest trade unions will join him in a few months time in presenting the petition to Downing Street to demand the release of documents relating to the trials.
"If this is democracy, you can kiss my arse," he said. "It's like a police state - all we want is the truth."
Officials from the Shrewsbury 24 Campaign said the e-petition site should be run by an independent organisation, with no Government involvement.