Christchurch International Airport Ltd (CIAL) announced the purchase of 750 hectares for the project in July.
CIAL is 75 per cent owned by the council through its holding company, Christchurch City Holdings Ltd (CCHL).
The protesters attended the city council's finance and performance committee meeting dressed in black and carrying grave markers.
Speaking for Extinction Rebellion Ōtautahi, David Goldsmith said it was hard to believe a new airport was being mooted in the middle of a climate emergency.
"No amount of sustainability greenwashing can hide the fact that increased flight capacity will mean increased emissions. Our elected representatives owe ratepayers an explanation for how this project can possibly be consistent with the council's declaration of a climate emergency."
Sara Campbell, also with Extinction Rebellion Ōtautahi, said the proposed airport development raises issues of equity and climate justice.
"Worldwide, 1 per cent of the population is responsible for 50 per cent of aviation emissions."
The controversial development has ruffled feathers with some locals in Tarras and with Queenstown mayor Jim Boult.