The anti-collusion campaigner Raymond McCord has become the first person from the unionist community to address the Sinn Fein Ard Fheis.
Raymond McCord addressed Sinn Fein's conference
He accused the DUP of ignoring evidence of collusion between the security forces and loyalist paramilitaries.
Mr McCord wore his father's Orange Order collarette as he gave his speech at the party's annual conference on Friday evening.
His son, Raymond Junior, was murdered by the UVF in November 1997.
He told the republican conference: "A year ago a report came out from Mrs O'Loan which proved collusion and Nuala O'Loan was a government appointee, and yet the DUP in particular have ignored it.
"There seems to be within the DUP thinking, a hierarchy of victims."
A Police Ombudsman's report last year confirmed police colluded with loyalists who were behind more than a dozen murders in north Belfast.