The row over Northern Ireland electricity prices is expected to be referred to the Competition Commission, NIE said on Tuesday.
The company said it cannot accept proposals from Utility Regulator Shane Lynch which will determine how much it can charge customers in the future.
“NIE has not taken this decision lightly,” a spokeswoman said. “It has worked diligently throughout the price review process, which has been ongoing for over two years, in order to provide a robust business plan with extensive and detailed supporting information to facilitate the Utility Regulator to determine a price control that will enable NIE to provide an adequate service to its customers over RP5 and for the foreseeable future, and to finance its activities efficiently.”
NIE owns and operates the ageing electricity infrastructure across Northern Ireland and claims it will have to charge customers to replace the poles, pylons and wires over the next decade.
However, Mr Lynch who works on behalf of consumers, has said prices should be reduced.
Negotiations between NIE and the Utility Regulator have been going on since the summer.
An NIE spokeswoman added: “The allowances proposed by the Utility Regulator fall substantially short of the amounts required to enable NIE to meet its statutory and licence obligations and to carry out the necessary programme of work for RP5 to deliver the level of service customers expect.
“Moreover, the Utility Regulator’s proposals rely on regulatory arrangements which depart from the well-established system of regulation for network utilities that applies in the rest of the UK, notably in respect of their emphasis on ex-post assessments and retrospective adjustments.”
In a statement, a spokeswoman for the utility regulator said they would consider the NIE response.
She said: “The consultation on the licence modifications closes later today. We will take account of the NIE response, along with any other submissions that we receive, and our board will decide on next steps.”