A stuff-up of major sizes has seen Mercury Energy present radically discounted power to a great number of businesses in Dunedin that the corporation says was in fact meant for Dannevirke.

Mercury issued an act of contrition yesterday for the crusade, which started with cold calls to Dunedin businesses in the most recent month, the Otago Daily Times reported.

Companies were presented, over the phone, bulky discounts to leave their existing supplier and agree to two-year deals with Mercury.

However, those, who signed up, have been gotten into contact again by Mercury officials this week and told that the agreement was off since the discount was meant for Dannevirke, in southern Hawke's Bay, not Dunedin.

That was regardless of a number of business owners having verbal deals and written verification of the deal from Mercury.

One business owner had been given an offer of a 30 per cent discount, which amounted to $16,000 a year, and another a 45 per cent discount, amounting to $1200 for one year.

Mercury Energy Communications Manager, Marie Hosking while confessing a pricing fault said that it failed to account for local line charges that were meant for about 400 businesses that were offered incorrect quotes.