The South African mediator brought in to try to resolve the long-running Drumcree Orange Order parade dispute announced today his intention to quit.
Mr Brian Currin said that as Portadown Orangemen had withdrawn from the mediation process last month he felt unable to take it any further.
He said the Orangemen had cited a lack of trust in the rival nationalist Garvaghy Road Residents Coalition as the motivation for their withdrawal from mediation.
"In any mediation, where there is no trust there cannot be a successful process," said Mr Currin.
A review of the operation of the Parades Commission which has blocked the Orangemen from marching down the Garvaghy Road in recent years has already been ordered but will not report until next autumn, months after the marching season.
Northern Ireland politicians now appeared to have the immediate responsibility of resolving the dispute, said Mr Currin. He said he hoped that, in the circumstances, they would be able to do so.
However, Mr David Jones, spokesman for the Portadown Orangemen, conceded that there was little chance of a change in the ban on their parade ahead of when they march next July.
He said they had pulled out of the mediation process because very little had been achieved over more than two years and the process was now in a state of limbo.
PA