Allan Burns of Tesco Car Insurance says, "Unfortunately for motorists in the North West and London, high claim rates, car crime and sheer volume of traffic are forcing insurers to push up premiums in these highly urban areas."
By contrast, motorists in East Anglia are enjoying the country's cheapest car insurance (an average premium of £329), along with Scotland (£335), Wales (£365) and South West (£368).
Within regions, there are huge variations in prices offered by insurers - most marked in the North West, with a difference of £321 between premiums from the cheapest and most expensive providers.
Says Burns, "While motorists in the North West are paying above the national average, the good news is that they could save a significant amount of money simply by shopping around."
The study shows that average premiums for women continue to be cheaper than for their male counterparts, with prices for female motorists being on average 11% cheaper.