Motorists in Sheffield must now shell out Â£851 on average to insure their vehicles - a 16 per cent increase on the Â£734 they were paying this time last year.
In Doncaster, the average cost has accelerated even more sharply over the same period, from Â£634 to Â£746 - an increase of 17 per cent.
The hefty increases reflect rising prices nationally, with the average UK premium having increased by 14 per cent over the past 12 months to Â£838.
That is despite a small fall of one per cent during the last quarter.
The statistics were published today by the insurance comparison website Confused.com, which claimed it was more important than ever for drivers to shop around for the best deal.
It attributed the rise to a change in the way courts calculate compensation for victims of life-changing injuries. The 'Ogden' rate, which is applied to pay-outs to take account of the expected return on investments, was slashed in March from 2.5 per cent to -0.75 per cent.
Amanda Stretton, motoring editor at Confused.com, said: “With car insurance costs rising by 65 per cent over the last decade and 14 per cent in the last year it's no wonder drivers are dreading their next renewal date.
"The dramatic Ogden rate cut sparked a surge of car insurance price hikes across the UK, in an already inflating market, as insurers braced themselves to pay out more for personal injury claims.
"A recent government announcement regarding the way rates are set could increase the rate up to 1 per cent. This means insurers have been able to calm their pricing slightly this quarter. Even so, we expect this will be short lived given that prices have already started to rise again in September.
"Worryingly, there is every possibility that car insurance prices will be the most expensive on record during the first half of next year.
"Luckily, insurers are required to show drivers what they paid for their car insurance last year at point of renewal. Drivers wanting to make savings should take note of their renewal price and take a few minutes to get a comparable quote online at Confused.com, where they could save up to Â£289."