The Department of Agriculture has contested figures from the European Environment Agency (EEA) which suggest that the vast majority of tree plantations in Ireland since 1990 took place on bogland.
Environmentalists say the figures show that the forestry grant system, which was designed to take land out of farming, instead encouraged farmers to plant on ecologically-sensitive bogland.
Figures recently released by the EEA's Corine Land cover project, which used satellite images collected over the last 15 years, found that up to 84 per cent of new forest plantations since 1990 were on peatland.
Widespread forestry planting on bogland was one of a number of concerns raised by the Corine project, which found that the unprecedented development of the last decade had been taking place chaotically.
In relation to forestry planting on bogland, it was concerned about the damage to soil, water quality and water levels.
However, a spokesman for the Department of Agriculture said the figures were incorrect.
He said the proportion of new forestry projects on peatland was only a fraction of this. Its forestry section estimates that 30 per cent of recent forestry plantations were on peatland.
This figure is based on site visits to new plantations, he said.
"We're surprised at the findings, and we are taking it up with the EEA. These figures do not equate with the figures we have on the ground.
"We're also a little surprised that a satellite can determine what's peatland and what's not."
Friends of the Irish Environment, however, has claimed that research it has been carrying out with An Taisce suggests the level of planting on bogland is much higher than the figures from the Department of Agriculture.
"Our research would put the proportion at somewhere between the Department of Agriculture and the Corine figures, but definitely over 50 per cent," according to Mr Tony Lowes, of Friends of the Irish Environment.
Under EU grant schemes farmers are able to claim generous subsidies to encourage them to plant forests on marginal land as opposed to peat bogs.
Landowners are entitled to claim a one-off grant of just over €2,700 for each hectare of land that is planted with evergreen trees. They are then entitled to a premium of just under €210 per hectare per year for up to 20 years after that.