A new study says Ontario drivers may have overpaid billions of dollars in insurance.

The Ontario Trial Lawyers Association commissioned the Schulich School of Business study, which found that drivers likely overpaid by $3 to $4 billion between 2001 and 2013.

The study points to the profit benchmark set by Ontario's insurance regulator at 11 per cent return on equity as being too high.

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The authors of the study say the cap should be no more than 5.5 per cent, given low interest rates.

The Ontario trial lawyers are calling on the government to reduce the profit cap and they want the auditor general to investigate auto insurance in Ontario.

The Liberal government has promised to cut auto insurance rates by an average of 15 per cent from where they were in the summer of 2013 by this August.