The Tasmanian Government has been accused of failing to deliver a promised energy bonus on time.

In October last year, the state-owned Aurora Energy pledged to deliver $125 cheques for power bill relief for low-income households by Christmas.

Energy Minister Guy Barnett says 80,000 rebate cheques have been posted, but many have still not been received.

The Government has blamed a distribution error by Westpac for the delays in the delivery of the cheques.

The state’s Labor opposition then released a letter from the chair of Aurora Energy, Caryle Demarte, written on November 30, warning the Treasurer Peter Gutwein and the energy minister that pre-Christmas payments could not be guaranteed.

“It must be noted that there is a reliance on external parties Centrelink and banking partner Westpac to ensure timely distribution of the bonus,” the letter said.

“As such, we are unable to bind these parties to ensuring the payments will be made by December 20, 2017.”

The state’s Greens described the response as a “cop-out”.

“How can it be a cop-out when Westpac have put their hand up and said it was their mistake?” Treasurer Peter Gutwein said.

“Seriously, Westpac have made it perfectly clear. They have acknowledged that it was their mistake. They have said that they are going to fix it and that any outstanding cheques will be sent in coming days.”

A Westpac spokesperson says its distribution system will be reviewed to ensure such delays are not repeated.

Energy Minister Guy Barnett welcomed the bank’s apology.

“It's extremely disappointing, despite repeated assurances, that not all cheques were despatched by Westpac's mail distribution provider in the timeframe we were advised they had been,” he said.

“The point is that we were repeatedly assured that the cheques would arrive and would be sent out and get there before Christmas.

“And the point now is that Westpac have apologised, they had a distribution error and not all cheques were delivered.”