Domhnall O Cobhthaigh is leaving Sinn Fein to join the Socialist Party
A Sinn Fein councillor has announced his defection to the Socialist Party.
In a statement, Domhnall O Cobhthaigh said Sinn Fein now shares a "right-wing economic agenda" with the other main Assembly parties.
He added that he unambiguously opposed "all groups who would wish to take us backwards to conflict."
Mr O Cobhthaigh, who also resigned his council seat, is the fourth Sinn Fein member of Fermanagh District Council to leave the party in the past two years.
He described his decision to leave Sinn Fein as "very difficult" given the "many friends" he was leaving behind in Sinn Fein.
However, he said that the current economic crisis had brought difficulties to the party because of the "contradiction between the nationalist and socialist agendas within Sinn Fein".
He said the party was following policies of cuts and privatisation which would only cement sectarianism.
He added "Over the past year, I have come to understand that the Assembly system itself only reinforces the sectarian divisions within our society.
"All five mainstream parties are doing little more than overseeing the long-term administration of senior civil servants and their right-wing agenda.
"While I still have respect for many of my former colleagues within Sinn Fein, I cannot see how they will change this significantly in the context of the current framework of governance."
Domhnall O Cobhthaigh was co-opted to fill the council seat left by Poilin Ui Cathain who quit in March 2007 over Sinn Fein's decision to support the police.
Sinn Fein is seeking to co-opt another party member to replace Mr O Cobhthaigh on the council.
Local Sinn Fein MP Michelle Gildernew said they wanted to "avoid a by-election that would cost ratepayers £30,000".
"While I disagree with the arguments put forward by Councillor O Cobhthaigh and am disappointed to lose Domhnall from the team in Fermanagh, I respect his decision to step down from the council and resign from the party," she said.
The other Sinn Fein members to leave since 2007 were Gerry McHugh, Bernice Swift and Poilin Ui Cathain.