The family of an elderly couple wrongly accused by a vigilante group of cruising for prostitutes has complained to the Privacy Commissioner.

Auckland group Papatoetoe Reclaiming Our Streets wrote to Sally Hoani's elderly parents claiming their car was seen at night in an area "notorious for street prostitution".

However, Ms Hoani said her 83-year-old father was confined to a wheelchair and her 78-year-old mother lived in the Bay of Islands.

In the absence of a direct apology to her parents, Ms Hoani has laid a complaint with the privacy commissioner.

The group aims to chase prostitution off the streets of Manukau. One tactic is to send letters printed on pink paper to sex workers' clients.

The letter, sent to Ms Hoani's parents last July, was headed with her parents' car registration, which the group said had been placed on a public website and their details "handed to the appropriate authorities".

"Street prostitution only survives because of people like you," the letter said.