Figures for the July to September quarter showed 122 complaints were lodged, compared with 90 for the same period last year.

Of the 145 investigations completed during the three months, 47 - or 30 per cent - related to high bills.

Billing accounted for half the issues raised by complainants.

Energy Ombudsman Simon Allston also noted concerns about credit issues had more than doubled from 14 the previous quarter to 31.

``In particular, there has been an increase in complaints about pending or actual disconnections due to unpaid electricity accounts,'' Mr Allston said.

``This appears to reflect the difficulty some customers are experiencing with the combination of rises in electricity charges and winter accounts.''

Mr Allston said he was working with electricity retailer Aurora Energy and Workplace Standards to correct a ``significant system issue'' that was causing customers to be charged the wrong fees.

The Ombudsman's office has received 23 complaints about tariffs from customers in the past 12 months.

Mr Allston said the error usually occurred when construction of a new house was completed, but the electricity supply was not transferred from a general tariff to domestic rates.

``Over a period of time this can lead to a customer (often not the original customer) paying considerably more for their power than they should have done,'' Mr Allston said.

Aurora spokesman Richard Wilson said the obligation was on the customer and electrical workers to ensure they were being charged correctly.

Aurora has investigated imposing a penalty on electrical contractors who failed to get it right, but was unlikely to proceed.

Mr Wilson said an online portal had made it easier for workers to lodge the required paperwork.