From tomorrow, concession card holders, including pensioner, health care card and gold card holders will have to call their utility companies and give their details over the phone, otherwise the full amount will be printed on their bill.

Concession card holders will no longer be able to present their card and claim their concession when paying their accounts at Australia Post branches.

Kilsyth MP David Hodgett said the bill changes were a "sneaky, sly, crafty way for the State Government to save millions of dollars by not having to pay the concession discount".

He said up to 40 per cent of eligible concession card holders could be caught by the changes, "as the old utility bills acted as a trigger to remind people that they may be entitled to a concession on their utility account".

"These concessions allow certain groups in our community to pay for essential services such as water, gas and electricity at a cheaper cost. These concessions are also a direct budget outlay that have a significant impact on the State Government budget.

"It therefore raises suspicion when these changes are brought in from July 1, which may result in substantial savings to the Brumby Government. It begs the question, is the Brumby Government reducing their costs by stealth?

"It also begs the question, what is the Brumby Government doing to inform concession card holders of these changes from July 1?"

The State Government failed to respond by deadline.