Unionists attacked Sinn Fein after MLAs failed to agree on how an opposition at Stormont could be formed.
A committee report on Assembly structures showed Sinn Fein did not agree with the need for opposition.
The Assembly and Executive review committee concluded: "There is no consensus at present to move to a formal government and opposition model, such as exists in Westminster."
Ulster Unionist MLA Roy Beggs argued Sinn Fein had refused to back any changes during the work of the committee.
"It is disappointing that one party, Sinn Fein, did not engage constructively in trying to improve devolution in Northern Ireland," he said.
UUP committee members had at one stage argued for a referendum on the creation of an opposition.
But he said he would keep "working at it... because we do need and I think most people would accept and concede that we need an opposition".
Sinn Fein said it was content that an opposition platform is already automatically available to those who wish to 'opt-out' of the Executive.
Raymond McCartney MLA argued: "Some people approach the model of opposition as if it were an add-on to the system that we already have in."
The report also recommended that in future parties should agree the broad strokes of a Programme for Government in advance of the Executive being formed.