Politicians and union leaders are to step up calls for the Government to release all documents relating to the controversial case of building workers who have been fighting to clear their name for the past 40 years.
Actor Ricky Tomlinson was one of the building workers imprisoned in 1973 after being arrested for picketing following a national strike.
The so-called Shrewsbury 24 were arrested and charged under the 1875 Conspiracy Act, with six sent to prison.
Campaigners believe the arrests were politically motivated and have urged the Criminal Cases Review Commission to overturn the charges.
The Government has told surviving members of the group that documents relating to the case will be withheld for a further 10 years. The ban will be reviewed again in 2021.
Steve Murphy, general secretary of the building workers' union Ucatt, will join campaigners at a briefing in Westminster today, and will say: "The news that the Government papers will not be published for at least another 10 years is appalling.
"What they are hiding is a massive government conspiracy and shows that the home secretary of the day connived with the police and security forces at the behest of construction companies to make an example of ordinary workers."
Labour MPs and other union leaders, as well as Tomlinson, will join the event.