Dr Foskey was the ACT Greens representative for Molonglo from 2004 to 2008.

ACT Chief Minister Andrew Barr said a formal condolence motion would be held in the Legislative Assembly next week.

In a joint statement, ACT Greens leader Shane Rattenbury and Member for Murrumbidgee Caroline Le Couteur said Dr Foskey had a "fierce intellect" and had committed her life to sustainability, compassion and community.

Throughout the '70s and '80s she campaigned to protect forests in her home of East Gippsland.

As a school teacher Dr Foskey moved to Canberra in the 1980s and after completing studies at the ANU became the sole Greens MLA in the ACT Legislative Assembly when she was successful in her campaign in 2004.

"In her term, Dr Foskey worked incredibly hard on issues such as sustainability, and triple bottom line analysis - which has been a standard process when evaluating major ACT government decisions through the cabinet process for the past eight years," Mr Rattenbury and Ms Le Couteur said.

"She was particularly proud of her strong support for residents of the Narrabundah long-stay caravan park, ensuring that when the private owner sold the land the residents were not simply evicted but that the ACT government needed to step in and do a land swap with the owner to preserve the homes of those residents."

Dr Foskey returned to East Gippsland after her time in the ACT Assembly where she ran for the Victorian Greens in last year's federal election.

READ ALSO:

"It is a very sad day for the ACT Greens, and the Australian Greens, but we can all be proud of her achievements - both in the assembly, for the Greens, and in our communities - over her lifetime."

Dr Foskey is survived by her two daughters, Sam and Eleni.