Zest Car Rental managing director Rory Sexton said the new rules are being introduced by the Competition and Markets Authority (CMA) on January 1.

They are designed to ensure pricing is transparent and come in time for the peaks booking period in the new year.

In particular they focus on seven key areas including young driver surcharges, one-way fees, fuel charges, excesses and the cost of reducing them, pre-authorisations or deposits, collision damage waiver (CDW) exclusions and warnings about equipment extras like snow chains.

Sexton said: " The CMA’s new rules should have ensured that customers aren’t hoodwinked by cut-price headline prices, only to have extra charges piled on as they go through the booking.

“Unfortunately, it seems that some comparison services are interpreting the CMA’s rules more loosely than we have and I’m sure they’re not giving the level of transparency the CMA intended.

"Mandatory charges like young driver surcharges, one-way rental charges and fuel policy charges should be displayed from the very outset.

“These are not optional extras and will be added to the customer’s bill at some point. These extra charges along with eye watering Collision Damage Waiver insurance premiums can be substantial and if disclosed early on would most likely expose what looks to be a cheap deal to be something far less competitive.

“These types of shady practices give the car hire industry a bad name and these new CMA regulations were an excellent opportunity for the industry to clean up its act.

“I’m afraid from what we’ve seen just days before they come into force is some companies still trying to trick consumers with headline prices that are simply too good to be true.

“Unless these companies are planning a last minute switch over on New Year’s Eve, car hire customers will still need their wits about them in 2017 if they’re to avoid being fooled into paying more than they expected."