Aurora sent the letter to about 1300 large contract customers over the past week.

The letter explained there would be no change to the customers' energy costs despite the scrapping of the carbon tax.

In it, customers were told the likelihood of the carbon tax repeal had already been factored into their contracts.

An Aurora spokesman said a 7.8 per cent plunge in energy prices, received by about 270,000 Tasmanian customers at the start of the month, would not apply to this group.

``Unlike prices for residential and small business customers set by the (Economic) Regulator, wholesale electricity prices for these customers are determined by the market at the time of entering into the contract,'' the spokesman said.

``The wholesale energy purchase costs to Aurora for this customer segment will not reduce as a result of the carbon tax repeal, therefore there is no reduction for Aurora to pass on to customers.''

Bass Liberal MHR Andrew Nikolic urged Environment Minister Greg Hunt to refer the letter to the ACCC yesterday afternoon.

Mr Nikolic said it was critical for the competition watchdog to test Aurora's claims.

``My view is that the veracity of what the company is telling its customers should be tested by the ACCC,'' he said.

``The watchdog is there to test claims like these and ensure that every saving which should be passed on is.''

The Aurora spokesman said the company had consulted with the ACCC on the impact of the repeal and would continue to do so.

He said the company would not profit from the carbon tax repeal.