Any inquiry into the Bloody Sunday killings should include the role of Martin McGuinness, First Minister Peter Robinson has said.
The Sinn Fein MP and Stormont Deputy First Minister was an IRA leader in Londonderry in January 1972, the month when the shootings happened.
Mr McGuinness earned plaudits last month when he shook the Queen's hand in a gesture of reconciliation and has moved to distance the IRA from blame for Bloody Sunday.
A report which confirmed the innocence of the 13 men shot dead by British paratroopers also claimed that Mr McGuinness gave wrong information about his movements that day and was probably carrying a machine gun but did not engage in "any activity that provided any of the soldiers with any justification for opening fire". A 14th victim of the soldiers died later.
Mr Robinson asked: "How could you avoid an inquiry into that and say that we're going to have an inquiry into the Army personnel that were there? The Deputy First Minister has openly admitted that he was in charge. If that was the case then there has to be an investigation if you're investigating the Army."
The Chief Constable of the Police Service of Northern Ireland, Matt Baggott, has said the inquiry involving up to 30 officers could take four years. Police have yet to set a start date. The PSNI and Public Prosecution Service reviewed the findings of the Saville Inquiry, which said none of those killed were armed.
Mr McGuinness said: "Lord Saville was very clear in his report into Bloody Sunday that the IRA had no responsibility for what happened on that day.
"I consider comments from unionist politicians today in the wake of the decision of the PSNI to investigate the events of Bloody Sunday as an attempt to divert attention away from the actions of the Parachute Regiment on that day. It is clear that they do not want to see the Paras investigated for murder."
Bloody Sunday was branded "unjustified and "unjustifiable" by Prime Minister David Cameron as he unveiled a landmark report into shootings which earned headlines around the world. The civil rights protesters were declared innocent by that report and soldiers were found to have opened fire in the mistaken belief that they were under threat.
The Saville Inquiry, which lasted seven years, cost an estimated £200 million, but the findings cannot be used as evidence in the police probe announced on Thursday. The Northern Ireland Director of Public Prosecutions was not involved in the decision to launch the murder investigation, his office said.