Loyalist spokesman David Campbell has claimed he was monitored by an alleged IRA spy-ring at Stormont 20 years ago.
Mr Campbell spoke out after the publication of a Police Ombudsman report into the 2006 murder of republican informer Denis Donaldson.
The now defunct Real IRA later claimed it was responsible.
In her report Marie Anderson found no evidence that the PSNI leaked information about the former Sinn Féin official's whereabouts prior to his killing in April 2006.
However, she concluded that police should have carried out a further risk assessment when media reports revealed Mr Donaldson was in hiding in Co Donegal.
In 2002 Mr Donaldson was one of four people arrested after an alleged spy-ring was exposed at Stormont.
Charges against all the accused were later dropped.
Mr Campbell, who is a former Chief of Staff to ex-First Minister David Trimble, last night said he was being watched by the alleged spy-ring.
"As one who was a recipient of police warnings that my movements and activity was being monitored by the spy-ring at Stormont the real investigation should centre on who conducted the spying on many of us, for what purpose, and how did Sinn Fein think that activity was consistent with their support for the Belfast Agreement and the pledges of office taken by their ministers at that time," he said.
