The belief is disclosed in an 11-page document sent last month by the Irish government to the Northern Ireland Secretary, Mo Mowlam, pressing for a full public inquiry into the 1989 loyalist killing of the Belfast solicitor Pat Finucane.
The document, which has been seen by The Independent, says that new evidence received by the Irish government includes copies of what appear to be papers "originating within the British security and intelligence establishment".
The Dublin document says the new evidence includes allegations that named officers in the Royal Ulster Constabulary procured the murder of Pat Finucane, and that RUC Special Branch had detailed advance knowledge of the murder plot.
It adds that there are patterns "which tend to confirm widespread suspicions that elements in the security forces were used, at the expense of the rule of law, to prosecute a campaign against those deemed enemies of the state and to conceal what that entailed and who was culpable".
This assessment, which was clearly intended to remain private, comes at a most sensitive time for policing in Northern Ireland. During the summer the former Hong Kong governor Chris Patten is due to deliver a report on the future of policing in Northern Ireland. This will clearly have profound implications for the RUC.
Nationalists and republicans are already pressing for sweeping changes, while Unionists are trenchantly defending the force. The handling of the Finucane affair is often cited by critics as an illustration of why far-reaching change is necessary.
The RUC has also been heavily criticised since the killing of another defence solicitor, Rosemary Nelson, in March of this year. The investigation into her death is headed by an English police officer rather than an RUC officer.
The Irish government has already publicly called for the setting up of a public inquiry into the Finucane case, but this document reveals the extent of Dublin's suspicions. In addition to the speculation that elements of military intelligence and RUC Special Branch colluded in the Finucane murder, the document voices suspicions of intelligence involvement in many other killings.
It cites evidence from military intelligence files and from the diaries of Brian Nelson, an army double agent who had infiltrated the Ulster Defence Association, suggesting that Nelson was involved in 15 murders, 15 attempted murders and 62 conspiracies to murder.
Although the Finucane killing took place 10 years ago, the incident has continued to generate controversy ever since. Last month a United Nations human rights investigator, Dato Param Cumaraswamy, repeated his call for an independent judicial inquiry. He said he was "even more convinced now that there is a stronger case made out for a royal commission into that murder to ascertain whether there was security forces, including RUC, collusion".
The RUC called in John Stevens, Deputy Commissioner of the Metropolitan Police, to reopen the Finucane case last month. Mr Stevens, who some years ago conducted an investigation into alleged collusion, is heading a team of 20 English detectives. But campaigners say a public inquiry is required.
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