The introduction of joint authority to replace Stormont would be a "constitutional nightmare and politically eruptive" a leading politics academic has claimed.
ueen's University professor Rick Wilford was commenting after SDLP leader Colm Eastwood said that his party will not accept a return to Direct Rule from Westminster, and that only joint authority will be acceptable to nationalists.
If the Assembly cannot be revived, the SDLP chief said joint authority between the Irish and British Governments would be "the only acceptable position for the nationalist community".
Mr Eastwood raised the matter during a meeting with Secretary of State James Brokenshire, and has indicated that he plans to hold a series of meetings in Dublin where he will make a case for joint authority.
But Professor Wilford said joint authority is only thinkable as a theoretical exercise.
He said joint authority can be described as a greener version of direct rule.
London would retain sovereign authority over Northern Ireland but Dublin would have a consultative role in co-operating with Westminster over Northern Ireland affairs.
However, under joint sovereignty, Northern Ireland would be governed by London and Dublin together.
That would require a change to the Irish constitution and new legislation to be passed by Westminster.
"Joint sovereignty would be, in effect, an admission of failure by a UK Government," he told the Belfast Telegraph.
"Joint authority is a considerable step away from that, but nevertheless would be an admission that the current treaty arrangements between London and Dublin hasn't worked as well as perhaps everybody had hoped for.
"It would weaken the relative autonomy enjoyed by our local politicians within a devolved Northern Ireland because it would bring another actor on to the stage, namely Dublin.
"I don't think the unionists, nor at this stage London or Dublin would be terribly enthusiastic about going down that path (of joint authority).
"What they are going to try and do is get devolution back up and running.
"I think they are content, particularly Dublin, with the role they already enjoy through the various institutions which were created in 1998 and have been sustained ever since - such as the North South Ministerial Council and the British Irish Council - which does give Dublin a role in relation to the discussion of Northern Ireland affairs, but it stops short of the UK Government giving up on Northern Ireland, saying we can't do it ourselves."
Professor Wilford said he believes the focus of talks will be on tweaking current devolution institutions.
"Joint authority would certainly not be welcomed by unionists because it would give a greater say for Dublin over matters within Northern Ireland than it already enjoys, and I really don't think that Dublin wants to entertain that possibility anyway," he said.
"Partly because of the political ramifications there would be within Northern Ireland, and really their minds are focused on trying to tweak the institutional arrangements, because I think reform is on the way in relation to our devolved institutions.
"I think they (the British and Irish Governments) want to try as best they can to effect some agreement which enables devolution as we know it to be put back on track with the potential for some changes down the line like an Irish Language Act, maybe getting rid of the Petition of Concern or by getting rid of the deputy First Minister title and just having Joint First Ministers."