The Democratic Unionist Party is expected to challenge formally the right of the small Progressive Unionist Party to attend talks when they resume at Stormont on Monday following the summer break.
The PUP has close links with the paramilitary Ulster Volunteer Force, part of the Combined Loyalist Military Command (CLMC), which last week threatened UVF dissidents Billy Wright and Alex Kerr with "summary justice" unless they left Northern Ireland.
Ian Paisley, the DUP leader, said this week his party would not attend the talks unless the fringe loyalist parties repudiated threats of violence. Mr Kerr, a former south Belfast UDA commander, is in custody facing charges of helping organise a meeting of an illegal organisation.
David Ervine of the PUP has said the attack on the Kerr family was not ordered by the CLMC.
Yesterday's informal Anglo-Irish conference in Dublin was overshadowed by pessimism about the prospects of progress in the Stormont talks.
The Secretary of State for Northern Ireland, Sir Patrick Mayhew, acknowledged "a lot of damage" had been done by the events surrounding Orange marches. "Everybody understands that there is resentment, there is fear, there is revived prejudice," he said.
He conceded that doubts about the talks' future remained after Unionist procedural stalling in June and July. "If there is not a will to make things work they can't be made to work. But I believe everybody does want to make [it] work."
Meanwhile, both the SDLP and Sinn Fein condemned the action of DUP Mid- Ulster MP in appearing and speaking at a rally held in Portadown on Wednesday night in support of Mr Wright.
Brid Rodgers of the SDLP said Mr McCrea had made a highly inflammatory speech in a highly volatile situation.
Mr McCrea said he had been standing up for the democratic right of free speech.
A number of loyalists in south Belfast, including a prominent figure in the Ulster Defence Association, have been warned by police that their lives are in danger from the UVF in Mid-Ulster.