This is a warning for everyone who pays for car insurance - check NOW if you can slash the cost.

Do note, I haven’t said “if you’re at renewal”; it’s important to do this even if that’s many months away.

Car insurance prices have exploded over the last year, up 20% according to the AA index, while the Association of British Insurers' says 10%. And both predict rises to continue this year.

Yet by locking in on a cheap price now, that means those rises won’t affect you. Here's a tweet I got from Iain: "Just saved £375 changing car insurance MID-POLICY thanks to @MartinSLewis - thank you, man.”

For full help, see the my cheap car insurance system at moneysavingexpert.com/carinsurance, here’s the key need to knows.

1. Ensure you're on TODAY’S cheapest deal, then if prices rise, you're protected

If the predictions are correct and prices keep moving up, today's prices will soon look cheap. Plus many are overpaying already, especially those who just auto-renewed. Here's what to do:

AT RENEWAL? Then it's easy, just move to the next point.

RENEWAL WITHIN 60 DAYS? Some firms such as aviva.co.uk , Nationwide.co.uk and LV.com give quotes valid for 60 days so get one now, then check against quotes at renewal time.

As @dimuthuj7 tweeted: "@MartinSLewis. Renewal £521. Quote a month ago, which was honoured, of £319. Thanks."

MIDWAY THROUGH A POLICY? Follow the steps below to see if you can save a chunk by switching. If so, provided you've not claimed, for a £50ish admin fee (factor that in) you can usually cancel and get the rest of the year refunded.

You won't earn the year's no-claims bonus, but if it means you save now and prevent future price rises it can be a big winner.

2. Don't just use one comparison site, combine them

There's no one cheapest insurer, as prices are set individually. So the aim's to check as many quotes as possible, quickly and easily. Comparison sites do that, yet they don't all cover the same insurers or even give the same price for the same insurer, so use more than one.

My current order: Confused.com, Gocompare.com and MoneySupermarket.com. If you can, use all three.

3. Then check the biggies comparison sites miss

DirectLine.com, Aviva.co.uk and Zurich.co.uk won’t appear on comparison sites, but can be competitive especially if you've no convictions and a clean licence.

As @damianderby tweeted me: "Did your car insurance checklist and saved £100 (1/3) off my renewal. It was Aviva. Pays two go past the comparison sites."

4. Hidden hot deals comparison sites miss...

There are also special promo deals around, some of which aren't listed on comparison sites. These often mean you get say £60 Amazon voucher or free gifts with policies.

There’s a daily updated list of the hottest at moneysavingexpert.com/carinsurance.

If you’re a member of cashback websites you may also be able to get money back on the policy you’ve chosen.

5. Check multi-car policies if you've more than one car in the home

A few insurers offer special discounts if you have more than one car. It's always worth trial and error to compare these against standalone deals. Sadly comparison sites' tech doesn't allow this, so you need to do it manually.

Admiral.com Multicar gives discounts of up to 25% depending on how many cars you insure.

You can also get discounts by linking the household standalone policies with Churchill.com, DirectLine.co.uk and Privilege.co.uk.

6. Check if comprehensive is cheaper than third party

I know this doesn’t make sense. Yet merely selecting comprehensive means some insurers see you as a lower risk, and it lowers the price. So if you want the cheapest cover, check if comprehensive’s cheaper.

7. Adding extra drivers can cut your cost

Yes, covering more people can be cheaper. This is because if they’re a lower risk profile, it can bring down the average risk.

It’s especially strong if you're a young driver adding a responsible older driver, yet everyone should try, as forumite Bouncybubbles told us: "Quoted £900 from £500 previous year. By comparing then adding my husband I got it down to £298."

8. Legitimately tweak your job title

You can't claim to be the boss of Barclays if you're a 'butler in the buff' (or vice-versa) but many people have wide ranging roles.

Yet I once did a TV makeover for someone who saved £50ish by calling himself "bar staff", not "bar steward".

Fabsternation tweeted: "Changed from creative director to marketing manager - saved £300.”

9. 'Paying monthly' doesn't exist - instead it's a 107% APR loan

Insurers may call it paying monthly, but actually they loan you the year's cost and charge often hideous interest, sometimes above 100% APR.

So pay upfront if you can and, if not, try to get one of the many year-long-plus 0% credit cards (see moneysavingexpert.com/0%cards). Just ensure you pay it off over the year, then there's no cost.

10. Don't want to switch insurer? Haggle, haggle, haggle

This works best at renewal. Simply find the best price you can at speed and then ask your existing provider to beat or match it. Often it will.

Eddy emailed: "My car insurance renewal offer arrived, a shocking £345. A quick phone call achieved a reduction to £143 - not bad."

And don't be surprised if your existing insurer offers a far cheaper price as a new customer via comparisons than its renewal quote.

Martin Lewis is the Founder & Editor in Chief of Money Saving Expert.

To join the 10 million people who get his Martin’s Money Tips weekly email, go to moneysavingexpert.com/latesttip