It is to call for two independent inquiries - one into the alleged intimidation, and another into the 1989 murder of Belfast solicitor Pat Finucane, citing continuing suspicions of security force collusion in his killing.
The report, an advance copy of which has been obtained by The Independent, was drawn up for the United Nations Human Rights Commission. It is expected to be presented to the Commission in Geneva this week, possibly today.
Its far-reaching criticisms will provide a significant challenge for the Government and security forces, with its charges that the RUC systematically targets lawyers for intimidation.
The authorities will also not welcome the reopening of the question of the Finucane murder, which is regarded by many as a particularly murky case within the loyalist underworld. It has already given rise to many accusations of co-operation between elements of the intelligence community and the loyalist gunmen who killed him.
The report is the work of a distinguished Malaysian jurist, Param Cumaraswamy, who is the UN Human Rights Commission's special rapporteur on the independence of judges and lawyers. His visit to Belfast last October was the first ever visit to Ulster by a UN rapporteur.
The Government may well be disappointed that he delivered such serious criticisms despite being given unprecedented access to important figures such as the Lord Chief Justices of Britain and Northern Ireland, the Northern Ireland DPP Alastair Frasier and RUC Chief Constable Ronnie Flanagan.
The RUC last night responded sharply to his report, saying it fell short in terms of objectivity, accuracy and fairness. It added: "As a supposed fact-finding mission, it gives scant regard to measurable facts or evidence to support allegations."
Mr Cumaraswamy reported that he had spoken to a large number of solicitors and barristers engaged in terrorist-related cases, all of whom, he said, had corroborated reports of harassment and intimidation.
Lawyers had complained that police regularly abused them. They also said that detectives often told clients during interrogations that their lawyers were working for paramilitary groups rather than for them as individuals.
Rosemary Nelson, who represents Colin Duffy, a well-known republican, alleged she had been the victim of numerous death threats. She also accused an RUC officer of spitting on her face, and another of striking her on the back of the head with a riot shield.
The report said most lawyers believed making official complaints about such matters was futile since any investigation would be carried out by the RUC itself. It added: "Many referred to the harassment and intimidation as an occupational hazard that they had come to expect and accept."
The report cited statistics from the Independent Commission for Police Complaints. These indicated that in 1996, the lodging of 2,540 new cases of complaint had resulted in disciplinary charges against 10 officers, only one of whom was found guilty of abuse of authority. The ICPC yesterday confirmed these figures were correct.
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