A would-be supermarket operator expects a violent and vigorous reaction from the two major chains to any new significant new entrant to the sector.
Tex Edwards of Northelia has told the Commerce Commission's hearings into competition in the sector that a third major chain would need significant scale to be competitive.
He estimated it would need a 15 per cent market share, with up to 150 shops in major centres and a capital investment of $3.5 billion.
Edwards said a new chain could expect operating losses for its first three or four years.