Sinn Fein’s Alex Maskey denied the IRA was involved in the murder of former republican prisoner kevin McGuigan, and branded such speculation “unhelpful and unwelcome”.
Mr McGuigan was gunned down close to his home in the Short Strand in east Belfast on Wednesday night.
However, the TUV’s Jim Allister said if mainstream republicans are found to have had a hand in the slaying, the implications of that “must not be dodged” – including the dissolution of the current power-sharing arrangements.
Mr Maskey said on Thursday: “I don’t accept for one second that the IRA has been involved in this, it just does not register at all. What I am concerned about is unhelpful speculation.
“We will be meeting with the PSNI shortly and what we will expect from the PSNI is a thorough and speedy investigation into events which resulted in the murder of a Short Strand citizen which has angered and hurt not only people in the area but much wider afield.
“It should not be happening and it needs to stop. It is unhelpful and unwelcome for people to enter into speculation.
“Whoever caused this killing should be, and hopefully will be, brought to justice as speedily as possible.
“We are calling for calm, we are calling for respect for this particular family at this time in the midst of their grief.”
Earlier Mr Allister had said: “Given the apparently informed speculation that Kevin McGuigan was murdered in revenge for the killing of IRA commander Jock Davison the key question – of security and political significance – is what organisation would be minded to revenge the killing of an IRA godfather?
“The answer may be obvious!
“If what are termed ‘mainstream republicans’ were involved, then the implications for the supposed ceasefire, even disbandment of the IRA, Sinn Fein and the political arrangements must not be dodged.
“Invoking the blind eye approach of ‘the peace process’ to let IRA/SF off the hook will not only again expose the moral bankruptcy of that process, but the complicity of all who play their game.”