Allocations being offered to farmers and industry under the amended Emissions Trading Scheme could be worth $100 billion.
A bill amending the scheme is before a Parliamentary select committee and is expected to be reported back to Parliament by Monday.
Under the proposed changes, trade-exposed sectors would receive allocations of emissions units.
Sustainability Council executive director Simon Terry says the allocations, which he says are clearly subsidies, have a nominal value of about $100 billion at a carbon price of $50 a tonne.
Mr Terry says that is similar in value to eight years total Government spending on health.
He says it is simply not correct that forest credits the Government will receive under the Kyoto Protocol will mean the subsidies can be given out at no cost.
Mr Terry says Treasury's accounting does not include the future charges for when the trees are cut down.