Sinn Fein's chief negotiator, Mr Martin McGuinness, has been informed by the RUC that his life is under threat.
Mr McGuinness, a Sinn Fein Assembly member for Mid-Ulster, was told of the death threat by police as he left his home in Derry last Friday.
He has claimed the officers refused to tell him the source or nature of the threat.
"It is totally unacceptable that the RUC can treat threats against republicans in this cavalier manner.
"I intend to instruct my legal adviser to pursue the legality of the RUC's refusal to appraise an individual as to the extent to which his/her life is under threat," said Mr McGuinness.
An RUC spokesman would not comment on Mr McGuinness's complaint and said the force did not comment on the security of individuals.
