Holidaymakers have been warned to avoid making a costly, but common, mistake when travelling, which could see them make one part of their holiday 12 times more expensive.

Everyone travelling abroad this summer has been urged to avoid insurance excess waivers offered by car hire companies, which can cost up to 12 times more than alternatives.

Consumer group Which? said it found travellers could be charged as much as £199 at car hire desks for policies which are inferior to options available for just £16.

Rory Boland, editor of magazine Which? Travel, said: “All too often hiring a car abroad is an unnecessarily stressful experience, with travellers sometimes pressured at the rental desk into buying overpriced insurance policies that they don’t want or need.

“What our research shows is that you should never take excess insurance from your car hire firm, no matter how hard the sell.

“Buy an ERI either directly from an insurer or via your car hire broker.

“The top rated policies are a win-win. Not only are they significantly cheaper than anything offered by a car hire company, but they are also more comprehensive, meaning you have peace of mind should anything go wrong.”

Basic car hire insurance included in rental prices is usually subject to an excess, meaning holidaymakers could be charged the equivalent of hundreds of pounds for issues such as fixing a puncture or replacing a windscreen, according to Which?.

To avoid being liable for this, people can either purchase a Super Collision Damage Waiver (SCDW) from their car hire company or Excess Reimbursement Insurance (ERI) from car hire brokers and insurers.

Which? analysed SCDW cover provided by six major car hire businesses in Malaga, Spain, this summer, and compared it with several ERI policies.

On average, for a week’s cover in Malaga holidaymakers are being charged £177 for SCDW, while ERI costs £38 from a broker and £23 from an insurer, according to the research.

Which? also found SCDWs are “inferior”, with issues such as misfuelling or stolen keys not covered.