The Democratic Unionists and the SDLP have been hit by defections to rival parties.
Former DUP executive member Edward Hanna said he was quitting for the Ulster Unionists claiming the Rev Ian Paisley's party was "misleading the electorate and being arrogant".
The chair of the SDLP branch in Bangor, Andrew Muir, said he was joining the Alliance Party. He asserted that the SDLP was "on course to merge with Fianna Fáil this year", claiming the time was therefore right for him to "realign myself with a party in tune with the real issues facing Northern Ireland".
The DUP hit back against Mr Hanna, claiming he had been fully behind recent party decisions. An SDLP spokesman said he had never heard of Mr Muir until the weekend Alliance statement announcing his defection.
Mr Muir said in a statement his new party provided a "natural centrist home in the post-nationalist era" in which we now live.
"As a committed pro-European I will campaign within and outside the Alliance Party for a federal Europe devoid of ancient national boundaries," he said.
"My decision to leave the SDLP is, in no way, a personal criticism of Mark Durkan or the many exemplary SDLP councillors, Assembly members and MPs who continue to diligently serve their constituents. It is, on the contrary, a personal decision to realign myself in light of a changing society and a changing SDLP," Mr Muir said.
Alliance leader David Ford said: "Local people can see that the Executive is failing to deliver under the dominance of the DUP and Sinn Féin. Ulster Unionist and SDLP members have little influence, but are tied to Executive policies. Only Alliance is in a position to present a credible and coherent alternative to the Robinson-McGuinness agenda."