Anyone genuinely concerned over employer blacklisting of trade unionists would agree with GMB general secretary Paul Kenny that denying workers their union rights should be a criminal offence.

The Independent Police Complaints Commission admission that police have been at the heart of blacklisting thousands of construction workers confirms what most trade unionists have always believed.

Collaboration between employers and repressive forces of the state is rarely admitted, but circumstantial evidence has been overwhelming.

The fitting up of two dozen building trade unionists 40 years ago by the combined forces of the Tory government, employers, police and legal Establishment is still denied officially, but the facts speak for themselves.

Des Warren, Ricky Tomlinson and their comrades were guilty of nothing more than playing leading roles in a successful strike to persuade building employers to improve pay and conditions.

The powers that be were still smarting from defeat at the hands of the National Union of Mineworkers in 1972 and were determined to mobilise the power of the capitalist state to redress the balance of industrial relations.

Concerted efforts to criminalise trade unionism involved charging the 24 building workers with conspiracy to intimidate, against which it was all but impossible to construct a defence.

The facts that police were present at all building sites successfully picketed, that no violence was reported, that no-one was arrested and that the police commanding officer went so far as to shake Warren by the hand to congratulate him on the discipline and good humour of the strikers counted for nothing.

The judge told the jury helpfully that "conspirators" did not have to know each other or even to have met to be guilty of the crime.

Consider the all-encompassing nature of this charge compared with the thousand and one get-out clauses that enable exploitative bosses to dodge responsibility for crimes that result in death and injury to workers.

As Kenny points out, the law already "requires state forces to be neutral on relations between employers and workers and employers are by law bound to respect the civil rights of workers to seek help from unions."

But legality appears to count for nothing when ministers - specifically former home secretary Robert Carr - felt able to respond to a dossier from the building trade employers to initiate a conspiracy to destroy workers' rights.

Conspiracy charges were chosen because of the difficulty posed to the workers' defence and because they provided for limitless jail sentences.

What would it take to get the political and legal authorities to prefer charges against reckless and blacklisting employers for conspiracy to deprive workers of their right to health and safety at work?

Public awareness of the scale of the blacklisting scandal, aided and abetted by police, has grown in light of revelations in other situations.

The massive conspiracies and cover-ups related to South Yorkshire Police failure to protect Liverpool football fans at the Hillsborough stadium in Sheffield and the misrepresentation of the police riot against striking miners at Orgreave have removed the blinkers from many people's eyes.

This is not about individual wickedness or inadvertent breaches of procedure. It concerns class interests - the rich and powerful against working people.

Making employers pay a similar price for blacklisting in deprivation of liberty as that meted out to trade unionists who challenge their wealth, power and privilege would represent a tangible victory for the working class.