Australian Greens Leader Bob Brown says former Minister for Forests, Senator Eric Abetz, should reveal, and pay back, the cost to taxpayers of his use of office to hire barristers for federal intervention in the Wielangta case in the Federal Court.

Senator Brown said the cost would be huge. The initial court case was against Forestry Tasmania, not the Commonwealth, but in August 2005 the Howard government and state government applied to intervene in the case in support of Forestry Tasmania.

"Senator Abetz has used parliament to attack my role in defending the Wielangta Forest in the courts, and fund raising to enable this action. But Senator Abetz has an equal and opposite responsibility. Abetz should reveal the totally unnecessary cost to the public of the federal invention on the case which he hosted, and then repay the money - though a public appeal if he wishes," Senator Brown said.