The Green Party wants the sudden death of hundreds of birds in a Canterbury cemetery, to be investigated.

A narcotic used to kill birds, alphachloralose, is thought to be the reason for the killing of European greenfinches in Ellesmere Public Cemetery.

The Greens' Environment spokesperson Eugenie Sage says it's not good enough that no agency has stepped up to confirm the cause.

Ms Sage said these birds were just left to die in the cold, and she's writing to the Environment Minister about it.

"If in fact the birds have been poisoned and if it has been shown to be alphachloralose then as the SPCA it shouldn't be available freely over the counter."

She said the Selwyn District Council should investigate the deaths because it's in charge of the cemetery.