A son of IRA murder victim Jean McConville has said Gerry Adams threatened him with a "backlash" if he released the names of those he believed were responsible.
Michael McConville has said his family's fight for justice will go on after the Sinn Fein president was freed, but has maintained he could be shot if he disclosed the identities of suspects to police.
Adams, 65, was released from Antrim police station, pending a report being sent to prosecutors, after four days of questioning about the notorious 1972 killing of the mother-of-10 and other alleged links with the IRA.
McConville told BBC Radio 4's Today programme: "Gerry Adams says to me 'Michael, you are getting a letter of support from the republican people'. He says 'if you release the names I hope you are ready for the backlash'.
"I took it as a threat."
Adams has vehemently rejected allegations made by former republican colleagues that he ordered the abduction and killing under investigation - denials he repeated again last night.
The decision whether to charge him with any offence will be made by the Public Prosecution Service (PPS) at a later date after reviewing evidence presented by police.
McConville alleged the "threat" was made around the time a report being drawn up by Northern Ireland's then police ombudsman, Nuala O'Loan, into claims that his mother was an informer was close to being finalised.
The Sinn Fein president had brokered a series of meetings between him and members of the IRA.
McConville said he used to tell Adams what had happened in the meetings and warned him that he would release the names of those involved if O'Loan's report was disputed.
At that point he said the backlash was mentioned.
McConville said that "could" have meant a backlash against the peace process but said he took it to mean the "backlash from republican people".
Adams will refocus on election campaigning today as the political fall-out from his release from police custody continues to reverberate around Stormont and beyond.
The republican party is holding a European election rally in Belfast tonight, with a similar event planned in Dublin tomorrow, as Adams resumes the canvassing activities he claims his detention was designed to thwart.
The rapturous welcome Adams received in a west Belfast hotel on his first public appearance was in marked contrast to the angry scenes outside the police station as loyalists protested at the decision to free him.
There was disorder in the loyalist Sandy Row area of Belfast, with petrol bombs and stones thrown, though no one was injured.
The former MP for west Belfast and now representative for Co Louth in the Irish Dail criticised the police's handling of his arrest but moved to dispel any suggestion that Sinn Fein's commitment to policing had wavered in the wake of the affair.
His arrest on Wednesday triggered a bitter political row at Stormont, with Sinn Fein accusing an "anti-peace process rump" within the Police Service of Northern Ireland (PSNI) of orchestrating the detention with the aim of damaging the party ahead of the European and local government elections.
This was angrily rejected by political rivals, whose fury intensified when senior Sinn Fein figures indicated that their support for the police - a critical plank in the peace process - would be "reviewed" if Adams was charged.
Democratic Unionist Stormont First Minister Peter Robinson denounced those remarks as "bully boy" tactics.
Downing Street confirmed that David Cameron and Irish Taoiseach Enda Kenny spoke yesterday to discuss the situation surrounding Mr Adams' arrest.
Adams questioned the timing of his detention and said police had unnecessarily used "coercive" legislation to detain and quiz him.