The forestry industry has hit back at farmers and doctors who are fighting a tax break for tree plantations, saying they are peddling baseless claims.

Results of an Australian Tax Office review of the concession will be announced with next month's federal Budget.

Farmers say the plantation tax break is an unfair advantage, causing an excess of tree crops over other industries.

Frank Nicklason, from Doctors for Forests, says it heightens concerns about pesticides and herbicides.

"The triazine chemicals, atrozine and simazine are probable carcinogens," he said.

But Phil Townsend from the National Association of Forest Industries says the allegations are baseless.

"The evidence is quite contrary to some of the claims that are being made," he said.

Mr Townsend also says other industries use the chemicals in greater quantities.