Scottish drivers who fail to shop around before renewing their car cover could be missing out on some of the biggest savings available in an increasingly competitive market.

Across the UK as a whole, motorists collectively waste almost £2 billion a year by automatically renewing their insurance, often because they assume that the provider offering best value the last time they looked will remain the cheapest.

Most don't even bother to compare their renewal quote with the previous year's price, and three out of ten auto-renew, despite the fact that they could be throwing away several hundred pounds.

Insurers were this week told by the regulator not to enter into any restrictive agreements with comparison websites, which ought to make for better shopping around.

September is one of the most lucrative months for motor insurers, as the arrival of the new registration plate means a high turnover of new and used cars, triggering a glut of annual renewals.

Gocompare.com says UK drivers have typically been with their current insurer for three years and many have stayed loyal even longer.

Only 46 per cent check their renewal price against their previous premium, and 29 per cent - that is more than eight million people - sign up for another year ­without getting any other quotes.

Insurers are also under pressure from the regulator to include last year's premium paid by the motorist alongside the quote they are offering for renewal - most insurers cleverly don't do that at present.

The latest AA British Insurance Premium Index shows a record drop in the average quoted annual premium for comprehensive cover.

Its typical "shoparound" premium - which is based on an average of the five lowest quotes - fell by more than £30, or 6.1 per cent, to £504 in the three months to the end of June.

Over 12 months, the fall was more than £120, or 19.3 per cent, and, for the third quarter running, was the largest 12-month fall ever recorded by the 20-year-old index.

Lee Griffin of GoCompare.com said: "There's never been a more competitive insurance market, as falling premiums mean that there are potentially big savings to be made."

The site calculates that those who make the effort to compare prices could cut their costs by up to £222 a year.

And Scots could be among the biggest beneficiaries.

The AA says Kirkwall, Aberdeen, Perth, Lerwick, Inverness and Galashiels are among the UK's 15 cheapest areas for car cover.

Janet Connor, managing director of AA Insurance, explained: "The premium reflects the likelihood of a claim being made.

"In some urban areas, there is a much greater risk of a collision taking place or of car crimes such as theft of or from a vehicle, uninsured driving or attempts at 'cash for crash' fraud."

As a result, the AA's typical shoparound premium is £821 in Manchester and £922 in London, compared to just £252 in Kirkwall and £303 in Galashiels.

Drivers living in these and other low-cost Scottish postcodes who have previously failed to compare prices could be onto big savings by starting to shop around now.

When your cover is due for renewal, spend an hour or so online or on the phone getting quotes from a couple of comparison services as well as from individual providers that don't work with these services.

You may be able to reduce your premium by opting for third-party, fire and theft cover instead of fully comprehensive

But this could turn out to be a false economy if you need to make a claim.

Increasing your voluntary excess - the amount of any claim paid by the policyholder on top of the insurer's compulsory excess - may also cut your premium, but don't raise it to more than you would be comfortable paying.

A very important way to keep the cost of insurance down is to drive carefully. According to Moneysupermarket.com, motorists who have an accident judged to be their fault could see their premium rise by more than eight per cent the following year.

Kevin Pratt, the comparison site's car insurance expert, warned: "Claiming for either an 'at-fault' or 'not-at-fault' accident will affect your car insurance premiums, as when an insurer assesses a driver's risk profile, any history of accidents will probably mean the motorist pays more."

This can make it well worth paying a little extra to protect your no-claims discount.

Meanwhile, a conviction for drink driving or points for speeding or other offences will add significantly to the price you pay for years to come.

Pay for the whole year up front rather than in monthly instalments, as most providers charge extra for credit.

If you can't afford this, consider using a zero interest credit card - but make sure you clear the debt before the interest-free period ends.

And if you are changing providers, don't forget to let your previous insurer know in plenty of time that you don't want to stay for another year.

Mr Griffin warned that : "If you don't get in touch, they may renew your policy using an existing direct debit. And you could face a cancellation charge when you realise you've got two policies in force."