Published Wednesday, 19 December 2012
The commission accepted the move would have cut bills for consumers, but said slashing the value of the gas company was not in the long term interests of Northern Ireland.
However it did permit the regulator to deduct £14m from Phoenix Gas.
The ruling means household bills will on average increase by £11 a year, while businesses could find themselves paying tens of thousands of pounds extra.
Regulator chief executive Shane Lynch said: "We will now carefully consider the detail of the Competition Commission's final determination and any implications for the next Phoenix price control, which will be implemented from 2014.
"More generally, and consistent with our principal statutory objective and the principles of good regulation, we will continue to work with DETI and other stakeholders to promote the economic development of the gas industry in Northern Ireland.
"In doing this, we will both protect consumers and ensure that efficient investment is adequately rewarded."
The NI Independent Retail Trade Association welcomed the completion of the process and said the expansion of the natural gas industry is "critical".
Glyn Roberts said: "If Northern Ireland's private sector is to be in a position to compete with others in the UK and Ireland, then competitive energy, which can form as much as 25% of a company's operating costs, must be seen as essential. It is estimated that around 70% of Northern Ireland's population are still using heating oil.
"Given the relative immaturity of the gas industry in Northern Ireland, many of our towns still do not have access to a fuel which is substantially cheaper and cleaner than other more established fuels such as oil or coal."
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