She recently gave a public lecture titled "Is Emissions Trading Really the Answer?" at the University of Otago, as part of an energy studies seminar series.
A former party co-leader, Mrs Fitzsimons later took part in a "conversation" event, organised by the university's Centre for Theology and Public Issues, at the Otago Museum, last Friday.
The Government's proposed amended ETS legislation, the Climate Change Response (Moderated Emissions Trading) Amendment Bill, is before a parliamentary select committee, and public submissions close tomorrow.
New Zealand's clean green image abroad was highly valuable for trade and tourism, she said in an interview.
"It would be nice if we lived up to that reputation. We're in danger of losing it."
The answer was "taking really strong and effective action on climate change".
The Government's proposed amendment of the country's existing ETS legislation was "a huge step backwards" from the current legislation.
"They are weakening it and diluting it to the point where it will have virtually no effect in addressing climate change."
New Zealand had built "a great and deserved reputation", including for its early provision of votes for women, its anti-nuclear stance and for being a "reasonably straight-forward" participant in international affairs.
But she predicted New Zealand would be "copping a lot of international cold shoulders" at the key UN Climate Change Conference at Copenhagen late this year, because of our weakened ETS legislation and watered-down response to climate change, she said.
New Zealand also needed to introduce reforms to improve energy sustainability, such as strengthening public transport.
Our weaker stance on climate change risked encouraging other nations with much higher carbon emissions to also "backslide" on their international responsibilities, she said.
