Experts have warned that more than a million motorists could be at risk of serious accidents and prosecution after buying substandard used tyres to save money.
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Police have responded by waging a campaign against drivers caught with defective tyres. The number of drivers pulled over for using illegal tyres has soared 9 per cent since 2009.
Officers can impose roadside penalties of up to STG100 ($A179) and three penalty points for each substandard tyre.
Despite the law saying used tyres must be stamped "part-worn" to prove that quality control and safety checks have been undertaken, only two out of five people who bought second-hand tyres found them to be appropriately marked.
Inadequate tread can cause skids and significantly increase a vehicle's stopping distance and fuel consumption, according to a report commissioned by insurers LV.
Of the 23 million used tyres sold since 2009, a quarter did not meet safety requirements. The number of trading standards investigations into part-worn tyre dealers has almost doubled in the past five years.
John O'Roarke, managing director of LV car insurance, said: "In the current economic climate, motorists are understandably looking to cut costs wherever they can and buying quality used tyres is one way to do this.
"Unfortunately some second-hand tyres sold do not meet the legal safety requirements and are not fit for the road, putting motorists at risk of a criminal conviction or worse."
