The Sinn Fein president Mr Gerry Adams said it was an understatement to describe alleged British state collusion with loyalist paramilitaries as Britain's Watergate.
The British authorities viewed collusion as a vital part of its campaign against republicans, he said last night.
He also accused media and politicians of failing to properly acknowledge the suffering of those bereaved as a result of killings by the British army and the RUC over the period of the Troubles.
"When one considers - as the evidence proves - that the figure of those killed through collusion with loyalist death squads also runs into many hundreds, then the enormity of exactly what the state has been involved in during the conflict begins to impact." Those bereaved by such violence felt their suffering was being ignored, said Mr Adams. "The efforts of the state to ignore these cases, and the failure of the media and most of the political establishment to treat these cases as equally deserving of concern, has compounded the feelings of anger and alienation which many of the relatives of the forgotten victims share."
Referring to collusion, Mr Adams cited the case of Brian Nelson, the British army agent who was an intelligence officer for the UDA. His action resulted in many killings, including those of Belfast lawyer Pat Finucane, Gerard Slane and Terence McDaid, he added.
Delivering the Damien Walsh memorial lecture at St Mary's University College on the Falls Road he said loyalists killed Damien Walsh in 1993 using weapons imported by Nelson. "Very clearly collusion didn't happen by chance. It happened by design," said Mr Adams.
He said in 1970/71 the British government looked to "its generals and spooks" to achieve a military victory. Part of the British strategy was to liaise with, organise, train, and control loyalist paramilitaries who had the "common enemy" of the IRA. This was the context in which collusion took place, he said.
The Sinn Fein president said he raised the issue of collusion and Nelson at virtually all his meetings with the British prime minister, Mr Tony Blair, and would persist with his demand for an international inquiry into the killings that followed from such collusion.
"This will not be easily achieved," concluded Mr Adams.
