The Ulster Unionist Party has denied that unionists are "crafting secret deals" over the Ardoyne parade dispute in north Belfast.
SDLP MLA Alban Maginness claimed unionist politicians were "circulating papers amongst themselves" on deals to resolve the Orange Order march dispute.
But Ulster Unionist Party leader Mike Nesbitt dismissed the SDLP allegation.
Earlier this month, the government agreed to set up a panel to examine the 15-month deadlock over the march.
Since July 2013, the Ardoyne parade row has been the subject of nightly unionist protests in north Belfast which, to date, has cost more than £12m to police.
The dispute centres on applications by Ligoniel Orange Lodge to march along a stretch of Belfast's Crumlin Road that separates nationalist and unionist communities.
For the past two summers, the lodge has been refused permission to hold the return leg of its annual 12 July parade along part of the route.
In a statement on Monday, Mr Maginness said: "I understand, from the comments of the leader of the Ulster Unionist Party Mike Nesbitt, that unionists are circulating papers amongst themselves and crafting secret deals on how the Ardoyne parading dispute will be resolved.
"Let me tell them now that if their plan is to concoct another self-serving plot to get their own way on parading, then they are wasting their time," the North Belfast MLA added.
Mr Maginness told the BBC that he had not seen the paper but claimed that Mr Nesbitt had described it as a "unionist document".
"I am given to believe that, in fact, there are some contacts between the NIO (Northern Ireland Office) and the unionist parties on this issue," the SDLP MLA said.
Mr Maginness warned that the Ardoyne dispute was an "incredibly sensitive issue" and any secret deal could "inflame" the situation.
"Any solution to Ardoyne has to be open and transparent, it cannot be on the basis of a secret deal between the unionist parties and the secretary of state."
However, Mr Nesbitt told the BBC: "There is no secret deal in Ardoyne.
'Over the line'
"What there is, is a proposal from the secretary of state to set up a panel - the very thing that the Belfast Telegraph, not unionists, called for - which also recognises the difficulties that the Parades Commission feel about the wider implications of making determinations in north Belfast," the UUP leader said.
"There are meetings to try and get the panel over the line and get this inquiry up and running and that is the beginning, the middle and the end of what's happening."
At the beginning of October, Northern Ireland Secretary Theresa Villiers announced she was setting up a panel of academics and other community figures to examine the Ardoyne dispute.
The move was in response to unionist leaders, who three months earlier had demanded an inquiry into the issue, after the Parades Commission banned the return leg of the Orange Order march for the second year in a row.
Nationalist and republican politicians objected to the panel, saying it undermined the work of the Parades Commission.
In response to Mr Maginness's remarks, a spokeswoman for the NIO said they were not aware of any secret document.
In a statement, the spokeswoman added: "On 7 October the secretary of state announced her proposal for a panel on parades in north Belfast. The terms of reference for the panel were included in the press announcement.
"After her announcement, the secretary of state met the combined unionist delegation and subsequently wrote to them to provide clarification on points raised during the meeting. A copy of that letter has since been shared with the leaders of the five executive parties, including the SDLP."