Winter tyres and snow chains on hire cars, known as ‘winterisation charges’, are compulsory in some areas and can be up to £114.

iCarhireinsurance.com, the leading provider of stand-alone car hire excess insurance, researched the costs of five rental companies in seven European ski gateways (i.e., Geneva, Grenoble, Innsbruck, Barcelona, Turin, Sophia and Inverness) for a week's hire from 27 December 2014 to 3 January 2015.

It found the average 'winterisation' cost across the seven destinations was over £40, but could be up to £114 in Geneva with Avis, significantly increasing a customer's overall rental cost.

Paying the winterisation charge of almost £60 in Barcelona with Budget, for instance, represents an additional 30% on the original hire cost.

In Austria and Germany winter tyres are mandatory, yet despite this Avis levy a 'winterisation' charge of £25 in Innsbruck. Snow chains must also used, where instructed in mountainous areas, in France, Germany, Switzerland, Italy, Austria and Andorra (source).

The 'winterisation' cost is included in the rental price in some instances but this varies greatly, for example Budget did not charge extra in Geneva or Innsbruck but charged £57 in Barcelona, £40 in Turin and £24 in Grenoble. In Barcelona all five rental companies charged a 'winterisation' fee averaging £53.

"Car hire companies are well known for surprise snowballing costs at the rental desk," said Ernesto Suarez, CEO and founder of iCarhireinsurance.com. "Why each individual customer should be held to account for winter tyres that have been changed once for the winter season is ludicrous and is another example of hidden costs that can make the original rental price not such a good deal."