Former Australian and Tasmanian Greens leader Dr Brown criticised the environmental signatories to the Tasmanian Forest Agreement, saying they had ``lost their way''.

``They were outflanked by a good-cop, bad-cop routine from the logging industry,'' Dr Brown said.

Like federal Greens leader Christine Milne last week, Dr Brown refused to criticise Tasmanian Greens leader Nick McKim for passing the legislation, saying Mr McKim ``had handled a difficult situation very well''.

``Four of the five Greens in the Parliament went where their chief constituency groups wanted them to go, but those groups lost their way and handed a very difficult decision to the Tasmanian Greens,'' Dr Brown said.

Dr Brown instead suggested Premier Lara Giddings should have stood up to the Legislative Council, but she ``didn't have the stomach''.

Celebrated author and environmentalist Richard Flanagan added his voice, calling the deal ``perhaps the greatest own goal in Australian political history''.

``Astonishingly . . . the environmentalists' leaders have managed to split their own movement in a way that will take many years for it to recover from,'' Mr Flanagan said.

Mr Flanagan, Dr Brown and Senator Milne have pointed to the ``durability'' clauses, which attempt to limit protests in exchange for the best chance of securing crucial Forest Stewardship Council certification, as key reasons for their opposition to the agreement.

In a lengthy response to Mr Flanagan, Greens minister Cassy O'Connor said he had cast the four Tasmanian Greens in favour of the agreement ``with dark motive and hollow core without having once spoken to any of us about why we chose the path we did''.

``Your article contains errors of fact, incorrect assumptions and - in my view - unnecessarily divisive, personal language.  I reckon you should be taken to task for what is not one of your better efforts,'' Ms O'Connor said.