The National Party says it would allow forest owners to fell forests and plant them somewhere else without penalty.
The Government's proposed Emission Trading Scheme bill, which is expected to be passed by Parliament this week, would allow only for offsets of carbon emissions from forests if they are made part of the Kyoto Protocol in future.
Forest owners currently face deforestation taxes unless they replant on the same spot.
National says it would change the scheme so a pre-1990 owner planting an alternative area with the same carbon absorbing capacity would not face any costs.
It says it would make the change within nine months of taking office.