A Sinn Féin move to block the lighting up of Belfast City Hall to mark Northern Ireland's centenary has been upheld by council legal advice.
The DUP tried to illuminate the landmark building last October to coincide with a cross-community church service marking the formation of Northern Ireland.
Agreement was secured from most party group leaders in Belfast City Council, but the decision was halted after Sinn Féin used the 'call-in' process.
This can be requested if 15% of councillors believe a decision was not properly reached or would adversely affect a section of the community.
A lawyer is then asked to examine the decision to help determine whether it should be reconsidered.
Councillors have since received the legal advice, which it is understood found merit in the call-in on both procedural and community impact grounds.
It concluded the council's usual decision-making process of referring potentially contentious illumination requests to a committee had not been followed.
This was due to the request being received at the eleventh hour following administrative problems.
It was also noted that a decade of centenaries programme had previously been agreed by the council which did not include a lighting up of city hall.
The DUP had proposed lighting up city hall on October 21 after a dates clash prevented it joining a UK-wide lighting up of civic buildings the following night.
DUP councillor Brian Kingston, the party's group leader, criticised Sinn Féin's vetoing of the proposed illumination as "incredibly intolerant and narrow-minded".
He said it was unsurprising that the last-minute decision was "procedurally questionable under legal examination" but argued that all parties have "previously supported that procedure".
"The fact that Sinn Féin used the call-in mechanism to prevent the lighting of city hall to mark the Northern Ireland centenary shows incredible pettiness and their intolerance of any expression of unionist culture and identity," he said.
Sinn Féin has previously claimed the illumination plan was "political and triumphalist" and "disregarded" council procedures.
Councillor Ciaran Beattie, the party's group leader, said: "There is absolutely nothing to celebrate in the partition of Ireland for those from an Irish nationalist background.
"Partition is a hugely contentious issue that continues to negatively impact on our society and restrict the potential of our island to flourish."
The row followed Sinn Féin blocking Stormont's Parliament Buildings from joining the UK-wide lighting up of civic buildings as part of the British government's official Northern Ireland centenary commemorations.
Earlier last year unionist parties had also proposed placing a Northern Ireland-shaped stone at Stormont to mark the centenary, but the idea was again vetoed by Sinn Féin.
Unionists accused the party of a "shameful exercise" in vetoing the proposal, but Sinn Féin said the plan "reflected one political perspective".
A Belfast City Council spokeswoman said: "Legal opinion determined that the decision around the lighting up of city hall to mark the Northern Ireland centenary should have been subject to greater scrutiny via the committee process.
"A report will be brought back to members to agree a process around taking urgent, time-bound decisions."
