"I have given an undertaking to the corporations that they'll be no worse off," he said.

Premier David Bartlett announced on Monday that water and sewerage bills would increase no more than 5 per cent a year for the next three years, down from the original 10 per cent.

Between 15,000 and 20,000 Tasmanians had paid their bills in full before the change and those who have paid an increase of greater than 5 per cent on last year's water and sewerage charges will be due a refund.

Mr Aird was unable to say how much the Government would contribute to the corporations to assist with the administration of refunds.

"Once the implementation phase is completed we'll know that," he said.

Mr Aird also said Tasmanian Water and Sewerage Corporations chairman Geoff Willis's comments that it was highly unlikely the refunds would be distributed before Christmas did not contradict statements he made on ABC Radio on Tuesday.

Mr Aird said on Tuesday he hoped the implementation measures would be in place before Christmas and yesterday said that did not mean the refunds themselves would be distributed by Christmas.

Opposition treasury spokesman Peter Gutwein said the Government needed to review the water and sewerage reforms immediately.

"Rather than spending taxpayers' money to patch them up and get them through the election, what they should be doing is an immediate review," he said.

Mr Bartlett was out in the electorate again yesterday selling the changes.