The Competition and Markets Authority (CMA) has sent letters to car hire comparison websites, which are sometimes referred to as brokers or meta-search websites, to explain consumer protection law and to ask them to provide customers with key information about the rental.

The providers have been asked to make clearer these seven key areas to make the experience easier for motorists:

• young driver surcharges
• one-way fees
• fuel charges
• excesses and the cost of reducing them
• pre-authorisations or deposits
• collision damage waiver exclusions
• warnings about the need for snow chains (a legal requirement in some countries in winter).

The businesses have until January 2017 to make the changes and they must also write to the CMA to explain what actions they have taken. Once the deadline’s passed, the CMA said any companies not complying with the law risk enforcement action.

This latest initiative comes after the CMA last year told five leading car hire firms (Avis Budget, Enterprise Rent-a-Car, Europcar, Sixt and Hertz) to improve the way they deal with customers.

But as around half of all leisure car hire rentals begin with comparison websites, the CMA said this action will ensure consumers get transparent prices whether they book directly with a leading firm or through a comparison site.

James Macbeth, CMA project director, said: “The changes made by car hire companies earlier are already having a positive impact for holidaymakers hiring a car in the UK and abroad. However, we know that a significant amount of business is done through comparison websites and we are confident that by working with them we can ensure an even better service for motorists.

“Drivers will see a transparent ‘drive-away’ price – including every mandatory charge and any options they choose – before they buy. This will take away the surprise some feel when they only discover the real cost of their car hire at the rental desk.

“People will also get information about factors such as insurance exclusions, credit card pre-authorisations and fuel before they buy. This will make it easier to shop around, compare different providers and get the best deal.”

Tips to drive down the cost of hiring a car

1) Book in advance to save. Paying to hire a car in advance of your holiday can often save you money.

2) Check the fuel policy. Find out what the fuel policy is before booking. Do you need to return the car full or empty?

3) Check what you’re driving. Check the car for pre-existing damage and ensure the car rental firm marks this down. Take photos when collecting and returning the car – and don’t delete them after the trip. This is especially worth doing if you return the car before the rental firm is open and you just do a key drop. You don’t want to receive a bill for damage you haven’t caused.

4) Bring your own Sat Nav. Consider taking your own Sat Nav and child seat to avoid paying extra for these. If you do decide to get them from the hire firm, make sure you pay in the local currency rather than sterling as a poor exchange rate may be applied.

5) Get collision damage waiver. When you hire a car, the rental agreement should include cover if you have an accident and damage property or injure other people. However, check your rental agreement, as it may not cover any damage caused to the hire vehicle itself. It may be worth paying for collision damage waiver (CDW) so if you have an accident, you don’t have to pay for the whole cost of repairing damage to the rental car (although you may still have to pay an amount towards any repair costs, called an excess).