Ms Kedgley said she had once suggested setting up a cross-party group to examine how the culture could be improved.
"But this went down like a lead balloon, and nothing much has changed since then, so there's seldom constructive dialogue or thoughtful debate in this House, and much of the time no one is even listening to our debates."
The most constructive work was done away from the cameras, Ms Kedgley said.
"In Parliament far more energy is spent on spin, and on trying to win the daily media battle, than on grappling with the crises that confront us," she said.
Ms Kedgley also raised concerns about the "excessive" use of urgency, saying that by-passing proper public consultation fuelled a growing distrust of politics.
Former Green Party co-leader Jeanette Fitzsimons, along with former member Sue Bradford, were among the more than 100 supporters who turned out to hear Ms Kedgley's farewell speech.