Peaceful political protest is supposedly intrinsic to the democratic rights enjoyed by people in Britain as a result of centuries of mass struggle against entrenched power.

That right apparently doesn't apply if protesters direct their fire at a major participant in the blacklisting scandal that has disfigured the world of work, especially the building industry, for decades.

Who gave bully-boys masquerading as security at the Merrion Centre in Leeds the authority to launch thuggish attacks on peaceful protesters invited to a union office within the centre?

Just because rampant blacklister McAlpine has premises in the Merrion Centre does not mean it has the authority to treat the entire building as its fiefdom and to eject anyone it doesn't like.

Beating up members of the public and putting one of them, Unite activist Pete Shaw, in hospital is behaviour that normally lands people in court - except when violence is committed in the cause of corporate arrogance.

There has still been no comeback for the driver who speeded into an anti-blacklisting picket line outside the BAM site at Manchester City FC training ground six months ago, despite building worker George Tapp, in his mid-sixties, ending up in hospital with broken legs and a head wound.

Despite the efforts of David Cameron and his privately educated multimillionaire Cabinet members to tar trade unionists with the "violent thugs" brush, it is clear that the cap fits company bosses and their hirelings more snugly.

Construction companies have operated with impunity for decades, bankrolling groups such as the Economic League and the Consulting Association to draw up lists of "undesirable" trade unionists and deny them the right to work.

Westminster government failure to act decisively to stamp out this crime, to expose its perpetrators and to make them pay exposes its complicity with the blacklisters.

The Welsh government has shown the way forward, pledging to ban firms guilty of blacklisting from bidding for public contracts.

Welsh Finance Minister Jane Hutt's call for a "united front" on the issue and for a full public inquiry should be supported by all in favour of working people's right to play a role in economic life without being deprived of employment opportunities.

Scottish First Minister Alex Salmond's pledge to follow the Welsh example in ensuring that "blacklisting will not be tolerated" illustrates the breadth of campaign necessary to end the scourge that has blighted many people's working lives.

As Scottish TUC general secretary Grahame Smith makes clear, the thousands of trade unionists blacklisted by construction companies did nothing illegal.

Their unforgivable crimes consisted of raising normal trade union issues such as pay and conditions and, even worse, championing health and safety issues.

Corporate hostility to health and safety representatives reflects firms' obsession with profits.

Many companies would prefer to pay compensation - often derisory - to workers or their families in cases of injury or death rather than implement a safety regime that would make such occurrences less likely.

No wonder that an inhuman attitude to fellow humans' suffering leads to the scandal of blacklisting.

Both government and the Information Commissioner's Office have dragged their feet in dealing with this scar on the face of human rights in Britain.

Construction companies must end their delaying tactics and co-operate with trade unions to come clean on what they did, agree to stop blacklisting and pay appropriate compensation to those they wronged.