Faulty Takata airbags, which have been linked to deaths around the world, are being replaced by new faulty airbags, Australian consumer group Choice says.
The organisation said five carmakers had admitted swopping airbags for identical devices in Australia as a temporary fix.
Toyota said the replacements would be safe for several years because faults only emerged as the airbags aged.
But Choice said the policy left people "driving ticking time-bombs".
Japanese car parts maker Takata is facing billions of dollars in liabilities over its defective airbags, which have been linked to at least 18 deaths worldwide, including one earlier this month in Australia.
Some of the airbags contained faulty inflators which expanded with too much force, spraying metal shrapnel.
More than 100 million cars with Takata airbags, including around 70 million vehicles in the US, have been recalled since concerns first emerged in 2007. It is the biggest safety recall in automotive history.
Choice's investigation, which only looked at the Australia market, discovered that about 70% of the 2.1 million cars recalled in Australia had not yet been refitted.
It said Toyota, Mazda, Lexus, BMW and Subaru all admitted to replacing the faulty airbags with identical devices. Many other manufacturers had not responded to questions, it added.
In a statement, Toyota said: "This action provided safety for a number of years, however due to exposure to the environment over time, these airbags will need to be replaced again."
Last week Australian police linked a road death in Sydney to a defective Takata airbag.
They said a 58-year-old man was struck in the neck by a piece of shrapnel when his Honda CRV was in a collision with another vehicle.
The government's consumer watchdog, the Australian Competition and Consumer Commission said it would investigate the recall.